GAP A: extend PATCH /tasks/:id to support all five TaskStatus values
(open, in_progress, review, done, cancelled). Add reviewTask, cancelTask,
reopenTask helpers in taskService. Claim semantics preserved: in_progress
requires assignedTo. Board columns for review and cancelled now reachable
via the API.
GAP B: index fromRole/toRole/fromAgent/toAgent on handoff upsert. SQLite
migration guard adds columns to pre-existing DBs without data loss. Board
renderHandoffs shows "fromRole[@agent] → toRole[@agent]" via → arrow.
GET /handoffs now carries the routing fields in every index entry.
Tests: +14 (56 total, 21 files, all green). Covers every new status
transition, index field presence, board markup assertions, and a guard for
the claim-without-assignedTo 400.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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