feat(alerts): TASK 43 — native events & alerts (six unique animations) + chat parity

Replace the external StreamElements feed with NATIVE YouTube events per the creator's
2026-09-23 question.

Chat parity half:
- YouTubeChatService decodes ALL SIX liveChat/messages event types into
  ChatMessage.Kind (superChat/superSticker/newSponsor/membershipGifting/
  giftMembershipReceived/memberMilestoneChat) — the four formerly-empty overlay
  rows are real now — and re-arms its one-shot poll on the server's
  pollingIntervalMillis (streamList connection semantics; clamp 1000-6000ms,
  maxResults=2000). ParsePage internal static seam + ChatPage record for
  deterministic tests; optional HttpClient ctor seam kept; InjectSimulatedMessage
  (TASK 41) preserved.

Alerts half (creator rulings: one celebration zone, six UNIQUE animations, no
menus/polls, sub mention = chat row only, NO viewer count):
- New SourceType.AlertBox 'Stream Alerts' (one per layout, CanAddAlerts gate
  mirroring chat; idle = transparent).
- AlertRenderer: six distinct branded animations (SuperChat slide-up/shine/
  count-up, SuperSticker scale-pop, NewMember drop-in/flash, MemberGift slide-left/
  chip-fan, GiftReceived confetti, MemberMilestone rise/growth-bar), every card
  drawing the 'made with LlamaCasty!' brand line.
- AlertOverlayLayer: true component (Commit-G pattern) — queue (cap 10, drop tail
  never stall), 33ms UI ticker, cache-first RenderFrame + UpdatePreview,
  Advance(double) as the deterministic test clock; ChatEventKind.None rows never
  enqueue.
- Wired: resolver RenderAlertBox, _alertLayer ctor + dispose, LoadLayout previews,
  Add menu item (Controls/LeftPanel.xaml), TestSessionViewModel sims tagged
  (member->NewMember, superchat->SuperChat).

Good Dog ONE integration test: AlertLayerTests (RealApp STA, real WPF raster) —
ParsePage classifies all six kinds + cadence fields; None rows enqueue nothing;
six events play pairwise-distinct moving frames then drain to null.

Gate: clean build 0 warnings; full suite 316/317, the one failure
(LayerReorderPersistenceTests.RealMouseDrag) repros on the clean tree — the
known environmental class (real-mouse-drag no-ops with a game/fullscreen window
focused).

References (OBS/overlay ecosystem):
- streamList semantics: https://developers.google.com/youtube/v3/live/docs/liveChatMessages/streamList
- OBS alert-box pattern (designated celebration zone, idle transparent): creator-chosen model

HANDOFF.md

@@ -1,103 +1,81 @@
-# HANDOFF — 2026-09-23 (build #77 feedback round; LOG fixes all shipped; app likely running)
+# HANDOFF — 2026-09-24 (TASK 43 shipped: native events & alerts — creator said "go")
 
 ## Branch / Commit State
 
-`main` HEAD = **`d72949e`** (build-77 top-bar feedback: avatar/gear/cluster). Backlog:
-`ac6e67a` (end close-out), `18ab553` (health-poll), `e69db4d` (TASK 42), `bb5dcb4` (TASK 41).
-Pushed state at `197ee81` (36 commits ahead locally — push only at a sub-milestone / on the
-user's say-so).
+`main` HEAD = new commit for TASK 43 (native events & six-animation alert box); previous:
+`3a4e17c` (account zone world-independent), `cb75066` (YPP 403), `d72949e` (top-bar feedback),
+`ac6e67a` (end close-out). Repo is ~10 commits ahead of pushed `197ee81` — **push is the
+creator's call** (sub-milestone decision, not per-commit).
 
-**Working tree DIRTY — account zone made world-independent (creator 2026-09-23):**
+**Working tree CLEAN after this unit's commit.**
 
-```
- M ViewModels/MainViewModel.Streaming.cs   (ShowSignInButton = !IsConnected, ShowAvatarButton = IsConnected)
- M ytLive.Tests/TopBarModeTests.cs         (REC-world asserts: avatar stays, Sign In visible signed-out)
- M ai.md, TASKS/task-42, HANDOFF.md
-```
+## ⚠️ The unit that just shipped (this turn, creator said "go")
 
-Previous two hotfix units (audio-sync dot + YPP 403/statistics-string) are COMMITTED (`cb75066`);
-top-bar feedback COMMITTED (`d72949e`).
+The creator asked (2026-09-23) whether the app could use **native YouTube events instead of
+StreamElements**. Research pinned the API facts; creator rulings locked the product shape. One
+combined work unit ("go"), task filed as **TASK 43** (`TASKS/task-43-native-alerts.md`):
 
-## ⚠️ The account-zone unit (this turn)
+1. **Chat parity half** — `YouTubeChatService` now decodes **all six** `liveChat/messages`
+   event types into `ChatMessage.Kind` (the four previously-empty event rows are real now) and
+   re-arms its poll on the server's `pollingIntervalMillis` (streamList semantics; clamp
+   1000–6000ms, `maxResults=2000`).
+2. **Alerts half** — new **`SourceType.AlertBox`** ("Stream Alerts", one per layout,
+   `CanAddAlerts` gate mirroring chat): an OBS-style celebration zone, idle = transparent.
+   `Services/AlertRenderer.cs` draws **six DISTINCT branded animations** (SuperChat slide-up/
+   shine/count-up; SuperSticker scale-pop; NewMember drop-in/flash; MemberGift slide-left/chip-fan;
+   GiftReceived confetti; MemberMilestone rise/growth-bar), each card carrying the "made with
+   LlamaCasty!" brand line (free product placement per broadcast). `Services/AlertOverlayLayer.cs`
+   is a true component (Commit-G pattern): queue (cap 10) + 33ms ticker + cache-first
+   `RenderFrame` + `UpdatePreview`; **`Advance(double)` = deterministic test clock**.
+3. **Creator rulings baked in:** no menus/polls (asked once, held); free-sub mention = chat row
+   only, **no sub alert** (YouTube emits none); **no viewer count** (vetoed — demotivating,
+   weaponizable); six events = six unique animations, not a recolored template.
 
-Creator, clicking RECORD on the live build: "why do you make the youtube user icon go away?" — the
-TASK 42 one-surface bar had scoped the account zone to the Stream world ("Record world has no YouTube
-identity at all"), so arming REC dropped the avatar AND the bar height bounced with it ("really fucking
-annoying"). Fix: `ShowSignInButton`/`ShowAvatarButton` are now world-independent (`!IsConnected` /
-`IsConnected`) — the right column never pops in/out, bar height pinned. Test stays a child of Stream.
-`TopBarModeTests` updated: signed-out Record world shows Sign In; flipping back to REC keeps the avatar.
+**Good Dog:** `ytLive.Tests/AlertLayerTests.cs` (RealApp STA, real WPF raster) — ParsePage
+classifies all six kinds + cadence fields; playback never enqueues a `None` (sub-mention) row,
+plays six pairwise-distinct moving frames, drains to idle. **Gate: clean build 0 warnings,
+316/317** — the ONE failure (`LayerReorderPersistenceTests.RealMouseDrag…`) repros on the CLEAN
+tree (proved via `git stash` + rebuild + isolated run): a real-mouse-drag test that no-ops while
+a game/fullscreen window steals the mouse (the HANDOFF-documented environmental class).
+**NOT a regression — do not chase it in-app; close games and rerun if in doubt.**
 
-## ⚠️ The app is RUNNING, and that's the story of this round
+## Follow-ups queued (NOT done in this unit)
 
-Ac6e67a **could not be verified through the normal gate** because the user was *looking at the
-running app* (PID 17752) while it happened. `verify.sh` (clean build 0-warnings + full suite +
-scope check) **cannot run until the app is closed** — an in-place build fails the `apphost.exe`
-copy MSB3021/MSB3027 while the exe is locked. Compile gate used instead: `dotnet build` reaches
-the copy stage with XAML/markup compiling clean (only the 2 copy errors → code + XAML are valid).
-
-## What the user asked this round (live-launch feedback on #77, all XAML-only)
-
-1. **Avatar** much bigger — now 40×40 (was 26), CornerRadius 20, initial 20pt. Shows the streaming
-   account at a glance (113% bigger than the old 26 read).
-2. **Gear** moved further from the brand — margin 6 → 18 (a couple more "places").
-3. **Uniform 32-height cluster in the top center** — segments host Border, Start/Go Live, and Test
-   all `Height="32"` so the REC|ON-AIR switch + its actions read as ONE family ("so the user can
-   intuit their purpose"). Running world (reality line) intentionally untouched. **[COMMITTED `d72949e`]**
-4. **Audio-sync status light LOST** — `"AUDIO SYNC"` slider keeps its numeric tooltip; the green/
-   amber 8×8 dot was "what is the point" dead weight. `IntToSyncBrushConverter` + its resource +
-   TASK-22's "visual feedback" decision all retired with it, both docs updated in-place.
-5. **YPP refresh bug (this turn, "Seriously?")** — `channels.list?mine=true&part=statistics,
-   auditDetails,contentDetails` 403'd `insufficientPermissions` on EVERY real refresh since slice 1
-   shipped: the **`auditDetails` part alone requires the `youtubepartner-channel-audit` scope**
-   (MCN partner tooling the app must never hold; the "no re-consent / scopes suffice" slice-1 claim
-   was wrong). Fix: part list is now `statistics,contentDetails`; standing flags dropped from
-   snapshot→VM→drawer in favour of an honest "not exposed to apps — check the Earn page" row;
-   `channels.list` failures now log the response body's `error.reason` (the bare code hid this for
-   days); new Good Dog `ChannelStatsServiceTests` guards no-auditDetails + still-parses — which it
-   then used to catch a SECOND latent bug the 403 masked (statistics are JSON strings; `GetInt64`
-   throws → now the tolerant `ReadInt64`, ValueKind-first). Docs:
-   ai.md / TASK-39 / TASKS.md / MyMistakes all corrected. Cite:
-   https://developers.google.com/youtube/v3/docs/channels/list
-
-## What shipped before this round (all committed)
-
-- **`ac6e67a` end-of-stream close-out fix** — every 2026-09-22 stop logged
-  `transition(complete) 403 invalidTransition`; the blind POST raced YouTube/autoStop marking the
-  broadcast complete (`enableAutoStop=true` always set). `EndBroadcastAsync` now pre-flights
-  `liveBroadcasts.list→status.lifeCycleStatus` and skips the POST when already complete/revoked;
-  inconclusive pre-check still posts (backstopped); never throws. Good Dog:
-  `EndBroadcast_Verifies_LifeCycle_Then_Transitions_Complete_Never_Throws` (3 halves: live→GET+POST,
-  complete→skip, 403→error-string). Cite: youtube liveBroadcasts/transition errors table. **Full
-  suite 315/315** (audio-timing flake `Mix_HonorsProviderGains…` cleared on rerun); verify.sh clean
-  pass predates this round's XAML-only edits.
-- **`18ab553` health-poll fix** — `status.healthStatus` is an OBJECT, not a string; every session
-  start logged `requires an element of type 'String'`. Nested shape parsed (flat tolerated), banner
-  alive again.
-- **TASK 42** (`e69db4d`) + **TASK 41** (`bb5dcb4`) — one-surface top bar, Test Stream drawer.
+- **Creator report still open — not yet diagnosed:** "I still cannot post a chat message in the
+  TEST tab." The TEST drawer's Mock Chat Input posts a REAL `liveChat/messages.insert`; the fix
+  needs its own scoped unit.
+- **TASK 3 item 20 persistence half** — the canonical `RewardEvents` SQLite table +
+  `superChatEvents.list` (30-day) backfill + session-report rollup (the shipped alert path parses
+  events to `ChatMessage` in memory; the report reads that table once it exists).
+- TASK 3 item 16 (Text source) still open; TASK 40 units A/C/D queued; TASK 32–36 queued.
 
 ## Around the task (carried facts)
 
-- RealMouseDrag test no-ops while a game/fullscreen window steals the mouse (POE 2 seen 2026-09-22)
-  — close games before full-suite runs. AudioPipeline timing flake similar (load-dependent).
+- RealMouseDrag tests no-op while a game/fullscreen window steals the mouse (POE 2 seen
+  2026-09-22) — close games before full-suite runs. AudioPipeline timing flake similar.
 - Test-env trap: saved OAuth session loads synchronously → force `vm.IsConnected` in signed-in tests.
-- `subscriberCount` YPP slice 2 needs re-consent — do not merge with other units. Polar `$99/yr`
+- `subscriberCount` YPP slice 2 needs re-consent — do not merge with other units. `$99/yr` Polar
   must become one-time before launch. `MARCOM.md`/`MONETIZATION.md` gitignored — never commit.
-- The **`YppSnapshot.OverallGoodStanding` etc. columns now serialize false forever** (the API path
-  no longer populates them; schema kept stable for the analytics slice). Don't "restore" the
-  standing flags via auditDetails — see the MyMistakes recipe.
-- TASK 40 App Settings round: units **A (camera) → C (defaults) → D (accent)** remain; A's
-  SharedReadOnly control-write question = only genuine uncertainty.
+- Latent bug the YPP 403 masked: statistics are JSON **strings** — always the ValueKind-first
+  `ReadInt64` (MyMistakes recipe), never `GetInt64`.
+- New facts recorded: the chat feed IS the event feed (six types, no sub event); streamList is a
+  connection-semantics description of that same endpoint (pollingIntervalMillis drives cadence).
+- Every committed change needs a **close + relaunch** of the running app to be seen — running
+  builds are live; verify.sh can't run while the exe is locked.
 
 ## Next step
 
-1. **Run the gate on the account-zone unit** (declared scope: `ViewModels/MainViewModel.Streaming.cs`,
-   `ytLive.Tests/TopBarModeTests.cs`, `ai.md`, `TASKS/task-42-top-bar-redesign.md`, `HANDOFF.md`) —
-   `./scripts/verify.sh`: clean build 0-warnings + full suite + scope check. Then commit it
-   ("account zone is world-independent — avatar stays in Record world", code + docs in one).
-   Repo is 36 commits ahead of pushed `197ee81`; push decision is the creator's (sub-milestone).
+1. **Creator verifies the alerts unit on the next run**: Add → Stream Alerts, then (Test Stream
+   drawer) Simulated Super Chat / New Member — confirm the zone stays transparent at idle and each
+   event plays its own animation on the canvas and preview; a real Super Chat during the next live
+   run confirms the real path.
+2. Push decision is the creator's (repo ~10 ahead). If pushed, note the commit id in this file.
+3. When scoped: diagnose the TEST-tab chat posting report ("I still cannot post a chat message in
+   the TEST tab") as its own Good-Dog unit.
 
 ## Critical working rules (unchanged, still binding)
 
 - **Good Dog = ONE integration test per change.** Scope lock + `./scripts/scope-check.sh` before commit.
 - Windows dotnet host for all WSL builds (`/mnt/c/Program Files/dotnet/dotnet.exe`, quoted paths).
-- 0 warnings on real clean builds (verify.sh only, never incremental). One runtime model.
+- 0 warnings on real clean builds (verify.sh only, never incremental). One runtime model.
+- No menus/polls with the creator; decisions asked once then held; do the work, then report.