TASK 36: composite the branding credit into the output, not just the preview

The credit existed only as a WPF BrandFlashLayer TextBlock in the preview at
25% opacity on a 300s timer. A viewer of the stream or the recording never saw
it, so "free tier shows branding" was not actually being delivered. The frame
pump has carried an unused per-frame flashFrame slot for exactly this.

Reverses the documented "Pre-GA posture" (ai.md Monetization), which kept the
flash preview-only so test VODs stayed clean. Creator ruling 2026-09-26: the
free tier has to be honest advertising, so it now reaches the broadcast.

One rendered VideoFrame feeds BOTH the frame pump and the preview, so the
creator's view cannot drift from what viewers get. Spec: 500ms in / 1000ms hold
/ 500ms out, first credit ~5s after go-live then every rand(30s)+30s, single
unwrapped line at a random spot inside the frame every time, neon white core
with a feathered red/blue halo.

Neon recipe is derivative work, per AGENTS.md: bright core + feathered
multi-radius halo with R and B split in opposite directions, from
https://nudaui.dev/components/neon-glow (layered text-shadow falloff),
https://help.maxon.net/rg/en-us/Content/html/Blurs-and-Glows-chromatic-glow.html
("with no displacement, the green channel is all but invisible behind your
white text" once R and B are split) and the OBS obs-stroke-glow-shadow
"feathered stroke with user-defined size and intensity". Neon blue is #4d8bff
rather than the theme's #0f3460, which renders near-black as a halo.

Also fixes a PRE-EXISTING bug found on the way: FramePump's fully-static
shortcut stretched the cached bake and returned it, silently discarding every
per-frame overlay - the social bar and the alert ticker were already lost
there. SceneCompositor.Overlay is now internal (it copies before blitting, so
the bake is never mutated) and the shortcut composites overlays first.

The credit is deliberately NOT folded into SceneGraph.GetBakedBase:
SceneRegion.Matches compares element ids only, so a credit in the cached bake
would freeze there and never expire. Per-frame only, and Epoch is stamped
every read because the 8MB master buffer is recycled - without that the
paste cache would freeze a stale credit.

BrandFlashEnabled is now derived !IsPremium and non-assignable, and the
presenter re-checks the licence on every read, so a key entered mid-credit
cuts the advertisement on the next tick instead of letting it finish.

Tests: 10 new facts. 357 total, 356 pass; the one failure is the known
environment-flaky RealMouseDrag layer test (needs an uncovered desktop
session). Adds RealAppHost.RunAsync - a frame-pump test must await inside the
collection's shared STA thread or the whole suite deadlocks silently.

NOTE: scope-check.sh flags Helpers/InstanceProfile.cs, AppLog.cs,
TokenStore.cs, WebView2Manager.cs and InstanceIsolationTests.cs as outside
this commit. That is a false positive: it uses `git diff HEAD`, which cannot
distinguish a planned second commit in the same session from an unrelated
edit. Those files are the dev multi-instance unit, committed immediately
after this one - as is the InstanceProfile paragraph in ai.md, which shares a
file with the Monetization section corrected here.

TASKS.md

@@ -167,6 +167,24 @@
 
 ---
 
+## 1.0 gates (do these before the first shipped build)
+
+- **Kill the dev multi-instance affordance.** `Helpers/InstanceProfile.cs` is already entirely
+  `#if DEBUG`, so a Release build ships as `DataRoot => DefaultRoot` / `WebViewDataFolder => null`.
+  Nothing to do but *keep it that way* — and re-prove it:
+  `InstanceIsolationTests.TheAlternateProfile_IsConfinedToTheDebugBuild` (source-level, always runs)
+  plus a Release build in which the `InstanceVariable` **field** is absent from metadata.
+  ⚠️ Do NOT grep the binary for `YTLIVE_INSTANCE` — consts are inlined and appear in neither build.
+- **TASK 36 is now shipped** — the branding flash composites into recordings and the stream. Test
+  VODs from an unlicensed instance carry the credit; use a license key for clean captures.
+- Still queued from earlier: `scripts/publish.sh` (self-contained win-x64, no test artifacts,
+  Debug-only `InternalsVisibleTo`, no WPF trimming), and the `LlamaCasty.exe` assembly rename
+  (three pack URIs incl. `MainWindow.xaml:14` — do not rename `%APPDATA%\ytLlive`).
+- Decide the open business question: `OverlayHost.xaml` copy says Polar unlocks *alerts* too, but
+  alerts are not gated by `IsPremium`. Either fix the copy or gate the alerts — do not leave it.
+
+---
+
 ## YouTube Live API research facts
 
 See [`TASKS/research-youtube-api.md`](TASKS/research-youtube-api.md) — authoritative facts for v3 build.