Bookmark / tag / annotate valuable moments in Session Playback (human feedback channel)

[chigichan24]

Why

• Today there is no quick way for a user to mark a turn as "this prompt / response is worth reusing".
• That kind of mark is effectively human feedback over the session corpus — the strongest training signal we can collect locally.
• This issue is the concrete implementation plan that operationalizes Support manual feedback for session #11 (Support manual feedback for session).

What

• On any turn or block in Session Playback, allow:
  • ⭐ Bookmark (boolean)
  • 🏷 Tags (e.g. reusable, anti-pattern, trick) — free text plus suggestions from prior values
  • 📝 Short freeform note (optional)
• Persist the feedback. Start with localStorage; design the data model so it can later be exported to a JSON file under public/data/feedback/{sessionId}.json and version-controlled.
• Surface bookmark counts as badges on the session list and (eventually) on Knowledge Graph nodes.

How

• Decide the persistent format first: { sessionId, turnId, blockId?, bookmarked, tags[], note } is a reasonable starting shape.
• UI: a small icon cluster at the top-right of each turn / tool block. Tags use free text with autocompletion from prior entries.
• Update the analyze-sessions pipeline to ingest the feedback file (when present) and attach it to session metadata.

Relates

• Refines Support manual feedback for session #11 (the umbrella feedback issue).
• Feeds into the follow-up issue Feed bookmark / tag / note feedback into Skill synthesis as a human signal #24 — using bookmarks as a synthesis signal.