Search the archive of completed/cancelled tickets by title. Uses hybrid search (keyword + semantic similarity). Returns up to 10 best matches, each formatted as `[phase] id: title`. Use `get_ticket` with the returned IDs to inspect a matching ticket — by default a truncated view (header metadata in full, description capped at 500 chars, all but the three newest comments capped at 200 chars), or the complete un-truncated ticket with `full: true`. Often works better using multiple parallel invocations with differently worded queries.