- Popup: project dropdown (list_projects + settings_save defaultProjectId);
  switching refreshes the last-report card and panel link immediately.
- Recording stop no longer submits blindly: the buffer goes pending and a
  composer opens in the tab with title (prefilled) + description, Save
  (Ctrl+Enter, copies the share link) or two-step Discard; unanswered
  pending recordings auto-save after 10 minutes, and starting a new
  recording auto-saves a pending one. Composer survives navigation.
- WebM is now a square cursor-following crop (shared cursorCropRect helper
  with the GIF path), source dimension raised to 1280 so the 512px crop is
  native-resolution at DPR 1; full-frame 800px stays as fallback.
- e2e: second project + popup switcher asserts, composer save (typed
  title/description verified on server), keyboard-driven discard flow,
  ffprobe square-video assertions (512x512 VP8).

Co-Authored-By: Claude Code <noreply@anthropic.com>

The recorder now captures continuous screencast frames via the CDP
screencast API and encodes them into a silent WebM (VP8, ~15 fps, capped
at 800px wide) uploaded as recording.webm. WebCodecs VideoEncoder is not
exposed to service workers, so encoding runs in an offscreen document
(chrome.offscreen) fed by base64 frame batches over a runtime port; the
result is verified with a local <video> playback probe and falls back to
the cursor-following GIF when encoding or verification fails (Firefox,
old Chrome, broken output).

Root cause of the earlier corrupt output: webm-muxer silently produces a
broken file when the first chunk's timestamp is non-zero — media
timestamps now start at the first frame and the muxer uses
firstTimestampBehavior: "offset".

The e2e now validates the uploaded recording with ffprobe (vp8 codec,
positive duration) and still covers the GIF fallback path, console-step
dump, navigation survival and replay.

Co-Authored-By: Claude Code <noreply@anthropic.com>