Tasks: richer GitHub Issue timeline parity (status from/to, review threads)

[ReBoticsAI]

Summary

Follow-up after shipping Issue timeline activity + card sheet grouping (#297). GodMode now shows GitHub Issue timeline events (labels, assignees, Project add/status changed, close/reopen, rename, etc.) and Issue comments under the GitHub section of the card sheet.

Why not done in #297

The REST Issue timeline API often omits Project status from/to labels and Project titles on project_v2_item_status_changed / added_to_project_v2 events, so the UI can only say "changed the Project status" / "added this to a Project". PR review threads and review comments were already out of scope for #293.

Scope

• Enrich Project board activity lines when GitHub exposes from/to status (GraphQL timeline or improved REST fields)
• Optional: merge timeline + comments into a single chronological Activity feed like the GitHub issue page
• PR review threads / review comments (beyond Issue comments API), if still desired
• Document any App permission gaps

Out of scope

• Embedding the GitHub web UI
• Replacing GodMode-local activity

Acceptance

• Linked Issue cards show Project column moves with readable from → to (or documented API limitation)
• If review threads are in scope: PR cards show review comments or a clear empty-state with why not
• Docs note remaining gaps in docs/features/tasks.md

Refs

• Shipped: feat(tasks): GitHub timeline activity, sheet grouping, description Markdown preview #297 (timeline + sheet grouping + Markdown preview)
• Prior: Epic: Tasks kanban parity with GitHub Projects board (+ GodMode extras) #259 (board parity epic), Tasks: stop GitHub sync poll remount flash; show Issue comments in card sheet #293/fix(tasks): sync poll no longer remounts board; Issue comments in sheet #294 (comments + soft sync)