docs(history): document session recording, tray redesign, and roadmap sync

Add Session History and tray-recording-indicator coverage across the
docs and the marketing site, using four new screenshots:

- README.md: new "Session History" section
- CLAUDE.md / docs/architecture.md / windows/CLAUDE.md: history.rs,
  the session-based logging.rs rewrite, and the tray blink now
  documented in the architecture reference
- website: a "Session History" dialog card, two feature-highlight
  cards, and a "Recording, Right From the Tray" showcase section —
  each marked with a discreet "Coming in v1.38" badge since this
  hasn't shipped in a tagged release yet

Also flips ROADMAP.md and tools/sync-roadmap-issues.ps1's
session-history entry to done (clearly annotated as unreleased) and
runs the sync script, which closed #175.

Refs #175