Zoom: compose the box as a real 2x layer above the background (Unit: zoom layer + magnification proof)

Right-click now creates a transient ZoomSceneElement at z-index 1 whose pixels are a
genuine 2x magnified sample of the backdrop (live capture under art), composited into
stream/recording like any layer while the output crop stays the tier. All shapes are
centered on the click and clamped to frame; healed on load/scene-create, never persisted,
hidden from the layers list + element template (IsZoomLayer). BuildCompositorOptions is
now internal = always tier crop (test seam). ZoomFrameBuilder is a pure static sampler
(box/2 window centered on the box center, single-slot cache) proven by a banded-backdrop
test; LayerReorderPersistenceTests drag resolves rows by item since the collapsed zoom
row shifts container indices. Also books TASK 51 (webcam background Remove + Blur) and
syncs memory docs (HANDOFF, MyMistakes, indexes). Full suite: 405 passed, 0 warnings.

TASKS/task-51-webcam-bg-effects.md

@@ -0,0 +1,94 @@
+# TASK 51 — Webcam background effects: Remove + Blur (v1 requirement)
+
+> Catalog: [`TASKS.md`](../TASKS.md) — status and requirements live here.
+> **Booked 2026-10-08 by creator ruling** — *"we're doing the bg removal and blur for v1 - book it, Danno"*.
+> This **reverses** the 2026-10-05 "background removal: out of product" exclusion (TASK 3 item 19).
+
+**Status:** ☐ Booked — **v1 requirement**. Queued behind the zoom build (current in-flight work unit).
+
+**Goal:** per-webcam **Background Remove** and **Background Blur** on the live webcam layer,
+selected per element in its properties panel, composited into stream + recording like any
+other layer. No external downloads, no hardware requirement, works on any machine.
+Replacement backgrounds are **free via layers** — drop any element behind the webcam.
+
+---
+
+## Why this is now IN (and what changed)
+
+The 2026-10-05 exclusion was based on: an in-app AI model = a runtime, a GPU/driver matrix,
+per-scene lighting tuning, and "a vcam app does it free." The ruling is reversed because the
+delivery shape changed:
+
+1. **Bundled small ONNX model (~2–5 MB)** — MediaPipe Selfie-Segmentation family —
+   shipped in the installer/fixture (TASK 48 MSIX), executed by **onnxruntime** (CPU default;
+   DirectML optional later). No NVIDIA SDK, no GPU requirement, no per-client download.
+2. **Quality reality (creator):** a 720p webcam displays at ~15% of a 1080p frame — premium
+   segmentation quality is invisible at that size; commodity class is sufficient.
+3. **⛔ Ruled out: NVIDIA Video Effects SDK (VFX / Maxine, AI Green Screen + Background Blur).**
+   Works on RTX 2000+/R570+ only, and needs a ~1 GB user-side redistributable on first use.
+   Creator: *"I don't think I'm putting a 1gb download requirement on a client box."*
+
+## Constraints — non-negotiable
+
+1. **No external download at runtime.** Model ships in the installer. (Store policy 10.2.2 —
+   same posture as the ffmpeg bundling in TASK 48 item 1.)
+2. **No hardware requirement.** CPU path must work; DirectML is an optional accelerator.
+3. **Per-element (Meld-style), not global.** Each webcam element carries its own effect.
+4. **No feature gating.** Works for free users; only the branding flash is paid.
+5. **Scene change / webcam add/remove must not crash or stall the pump** — a failing model
+   run skips to passthrough, never drops the layer.
+
+## Out of scope for v1 (same engine later)
+
+- ❌ **"Remove chair"-style object selection / quality tiers** — not a picker engine
+- ❌ **Super resolution / denoise / prettify passes**
+- ❌ **Virtual camera output** — permanently out of product (no vcam)
+
+## 1. ☐ Engine
+
+- ☐ Bundle an ONNX person-segmentation model (MediaPipe Selfie-Segmentation class, ~2–5 MB)
+  into the app (csproj copy like `ffmpeg/`, or as an `Asset`). Verify license + THIRD-PARTY
+  notices (TASK 36 item 6 gate).
+- ☐ `onnxruntime` via NuGet. CPU EP by default; optionally DirectML EP later. Failing EP
+  init → passthrough, log once, never throw from the pump.
+- ☐ Blur = **separable in-app blur** (box/gaussian) over the masked background region. No
+  model needed for blur once the mask exists.
+- ☐ Remove = **alpha 0 outside the person region.** The compositor already alpha-blends per
+  element (`SceneCompositor`, source-over) — no compositor change expected.
+- ☐ Feed the **VideoFrame seam** (`Services/VideoFrame.cs` doc explicitly anticipates
+  *"every future capture source (screen, background-removed webcam) feeds the same seam"*):
+  the frame handed to BOTH the preview bitmap path and the compositor's
+  `_cameraManager.GetLatestFrame` is the processed frame. One processing point, two consumers.
+
+## 2. ☐ Config surface + persistence
+
+- ☐ `WebcamSceneConfig` gains `BackgroundEffect` (`None | Remove | Blur`) + `Strength`.
+- ☐ Persist via the existing `WebcamSceneConfig` table path in `LayoutStore.Save.cs`/
+  `Load.cs` (new columns + migration). Follow `LayoutStore.Migrations.cs` conventions.
+- ☐ Properties panel: effect dropdown + strength slider, per webcam element.
+- ☐ Replace-background affordance: **none in v1** — the creator drops any layer behind the
+  webcam. Effect preview must not obscure the fact that layers below still show through.
+
+## 3. ☐ Test seam (Good Dog — one integration test per unit)
+
+- ☐ Model-runner interface seam (like `CameraEnumeratorOverride`) so tests inject a fake
+  segmenter — no real ONNX inference in the test suite.
+- ☐ Assert the **processed frame reaches both consumers** (preview bitmap + compositor frame).
+- ☐ `None` = byte-identical passthrough of the raw frame.
+- ☐ `Remove` = alpha 0 outside person rect; `Blur` = background region blurred, person sharp.
+- ☐ Config → persistence roundtrip (per webcam element).
+- ☐ Engine failure → passthrough + single log, layer never dropped.
+- ☐ Real inference: **manual on the creator's box** (camera + lighting), not in CI.
+
+## 4. ☐ Sequencing
+
+- ☐ **Separate work unit AFTER the zoom build.** This file is booked + scoped; do not
+  co-commit it with the zoom work.
+
+## Related (not duplicated here)
+
+- [`task-48-distribution-msix.md`](task-48-distribution-msix.md) — the model ships in the
+  MSIX; bundled-binary posture established by the ffmpeg work.
+- `TASKS.md` Webcam cadence section — the "⛔ no background removal" line is superseded
+  by this ruling; the **judder/compositor cost work is unaffected and still heads its lane.**
+- `research-store-certification.md` — 11.12/10.2.2 posture; nothing here sends data off-box.