fix: store full opencode tool output and display it in session view

- Collector sender now supports Remote-User header for forward-auth
- OpenCode parser: store full tool output (was truncated to 120 chars + first line)
- OpenCode parser: generate fallback content for tool-only turns instead of empty content
- OpenCode parser: increase parse timeout to 5min for large DBs
- Frontend: show collapsible tool output in session detail below turn body
- Frontend: extract toolOutput from both opencode ({output}) and claude-code ({content}) formats

chore: track task file and dist update for search UI

chore: update TODO and dist after search UI merge

fix: add tool column to search table; remove conversation bleed from comments

feat: add search UI layer — SearchTable, SearchFilters, SaveSearchForm, route, and styles

feat: add search data layer — adapter, highlight helper, hook, and tests

docs: refresh README and TODO after search+opencode merge

README: add search, projects, stats, saved-searches to API surface table;
remove stale reference to unshipped search task
TODO: mark #3 reviewed, unblock #7

search: add /api/v1/search API and opencode collector parser

- Add FTS5 search repository with BM25 ranking, cursor pagination, and owner scoping
- Expose GET /api/v1/search with query, tool, host, since/until filters
- Add opencode collector parser reading from SQLite opencode.db
- Spike document recording canonical opencode storage format

Invariants: no schema migrations, no wire type changes, read-only search,
marker snippets (not HTML), invalid queries → 400 INVALID, parser interface
unchanged, collector state schema preserved, stats/react stubs untouched.

Reviewed: offset fix (message.rowid instead of time_created for progress marker),
all 22 test packages pass.

docs: refresh search and opencode plan

docs: conclude lethe collector task

collector: persist skipped-only parser progress

docs: record collector endpoint and outbox checks

collector: enforce outbox cap before replay

docs: record collector final fixes

collector: fix daemon drain and backfill start

docs: update collector verify notes

collector: preserve valid rows around ingest errors

collector: skip rejected rows after partial ingest

collector: add lethe-collector cli

collector: add polling source runner