Extension: popup UI, panel URL, icon fix, GIF tracks and track replay ...

- Popup replaces the auto-start picker: mode choice (element note /
  record steps), latest report card with open / replay / delete, web
  panel link; share links open at panelUrl (default :5173)
- Register the Phosphor font via the FontFace API — constructable
  stylesheets ignore @font-face, which left overlay icons empty
- Recorder tracks upload as one animated GIF (gifenc) instead of per-
  step screenshots; frames follow event pacing, UI hidden on capture
- Replay a recorded track from the popup: background opens the start
  page, re-executes click/input/url_change steps with original pacing
  and flashes the result in the overlay

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