docs: update HANDOFF + MyMistakes.md — take-23 stride fix landed, chat missing from recording, landmines refreshed

HANDOFF.md

@@ -1,29 +1,40 @@
-# HANDOFF — 2026-09-06
+# HANDOFF — 2026-09-08
 
 ## Branch / Commit State
 
-**`main` HEAD = `e002847`** — web transparency fix (take-21): feed full canvas to compositor.
+**`main` HEAD = `f6802c7`** — take-23: stride-correct CropBounds Fill rendering.
 
 ```
+f6802c7 fix(web): stride-correct CropBounds Fill rendering in compositor (take-23)
+84aa70f docs: MyMistakes.md — take-22 full fix for widget scale/position + transparency
+ed9d7c1 fix(web): CropBounds metadata + Fill-style scaling in compositor — transparent margins preserved, widget fills element rect (BROKEN — reverted)
+5ca9778 docs: update HANDOFF + MyMistakes.md — take-21 web transparency fix landed
 e002847 fix(web): feed full canvas to compositor — transparent margins reveal layers beneath (take-21)
 70db344 perf(camera): MJPEG negotiation before frame reader — camera drives at its best rate
-0f059ec docs: HANDOFF — #12 landed (element rasters), MJPEG next, web transparency spin-guarded
-6d11e8b perf(compositor): reuse per-element rasters in-place — take-16 GC-churn fix
-87509bc (origin/main) docs: restructure TASKS.md into a catalog — one file per task in TASKS/
+87509bc (origin/main) docs: restructure TASKS.md into a catalog
 ```
 
-**Pushed to origin: `87509bc`.** 4 unpushed commits after it.
+**Pushed to origin: `87509bc`.** 7 unpushed commits after it.
 
-**`today-slices` branch @ `ce87490`** — preserves 17-commit chain. Fallback recovery.
+## Web Overlay — Current State
+
+take-22 (`ed9d7c1`) BROKE the widget — the CropBounds stride was wrong (pixel index used `w = cbW` crop width instead of `src.Width` canvas stride, reading garbage from the full-canvas buffer). REVERTED by the take-23 revert of `ed9d7c1`.
+
+take-23 (`f6802c7`) is the correct fix:
+- `VideoFrame.CropBounds?: (X,Y,W,H)` — metadata on the frame
+- `WebView2Manager` sets `CropBounds = (cropX, cropY, cropW, cropH)` on the LatestFrame
+- `BlitContentRaw` detects CropBounds and uses Fill-style scaling (stretch to cover, no aspect preservation) using `src.Width` (canvas stride = 1920) for ALL pixel buffer indexing — not the crop width
 
 ## Resolved this session
 
-- **Audio regression (TASK 26):** Non-event — external headset volume control was at minimum, not a code bug.
-- **Webcam black square / web overlay transparency:** FIXED at `e002847`. Root cause: `bccdb48` introduced alpha cropping; the CROP was fed to the compositor, which `UniformToFill`-zoomed the opaque content to cover the entire element rect. Fix: feed the FULL `1920×1080` canvas to the compositor; transparent margins reveal layers beneath; the alpha crop (`outPixels`) is used only for the preview `WriteableBitmap`. `0f441d8` (take-19) had the right insight but introduced `CanvasRing` alongside the fix — the ring reuse caused additional breakage. Take-21 keeps the single `CanvasScratch` buffer (no ring), feeds full canvas, Epoch increments per frame.
+- **Audio regression (TASK 26):** Non-event — external headset volume control was at minimum.
+- **Web overlay scale/position + transparency:** take-23 at `f6802c7`. The stride fix was critical — take-22 used crop width (e.g., 800) instead of canvas stride (1920) in pixel indexing, reading garbage from the full-canvas buffer and destroying content.
 
-## MyMistakes.md update needed
+## Still open (needs your run + log)
 
-The spin-guard entry for the web overlay needs updating with the take-21 resolution. See that file.
+- **Chat overlay missing from recording:** Chat shows in preview but not in recorded output.
+- **Audio/sync issues:** unspecified, no log yet.
+- **Webcam/capture speed:** unspecified, no log yet.
 
 ## Landmines