Phase 3 acceptance: record the 60-second propose/accept/undo demo

[Astralchemist]

The Phase 3 definition of done per docs/phase3plan.md §5 is a 60-second screen recording of:

1. `rig init && rig index` on a fresh TS project
2. `rig serve --all`
3. Open http://localhost:7474/map + Claude Code in another window
4. Click `authStore` node in the map
5. Type "what other concepts pull on authStore?" in the chat panel (or chat with Claude Code directly with rig MCP installed)
6. Within 10s two dashed edges appear with rationales
7. Hover → see rationale → Accept → dashed becomes solid
8. Reject the other → fades out
9. Click "Undo" → accepted edge reverts to dashed
10. Total under 60 seconds

Automated coverage is in place — `bun scripts/demo-phase3.ts` runs all 13 checks (propose → accept → WS events → REST → undo → restore). The video is the human-driven proof for the ship narrative.

Pairs with #2 (Phase 1 live demo). Once both videos are in hand, tag `v0.3.0-phase3`.