v5.8.4

Fixed

• tasks.json atomic optimistic locking (#331) - Concurrent /next-task and /ship runs could silently lose claims or leave stale registry entries due to unguarded read-modify-write on tasks.json. Fix uses _version + per-write _writerId optimistic locking (mirrors existing flow.json pattern): write atomically via rename, re-read and verify both fields match before declaring success, retry up to 5× with jitter on mismatch.
• tasks.json schema unification - worktree-manager wrote { version, tasks[] } while workflow-state.js read { active }, causing claim exclusion in discover-tasks to always return an empty set. Unified schema is { active, tasks[], _version, _writerId } with on-read normalization of both legacy formats — no migration needed.
• Silent corruption risk - readTasks() now throws on corrupted JSON instead of returning a safe default, preventing updateTasks from silently overwriting potentially recoverable data.
• Agent prompt raw file writes - worktree-manager Phase 6 and Cleanup Reference replaced inline fs.writeFileSync with workflowState.claimTask() / workflowState.releaseTask() library calls that are atomic and retry-safe.

Added

• updateTasks(mutatorFn) - optimistic-lock loop for tasks.json mutations (mirrors updateFlow)
• claimTask(entry, projectPath) - atomic upsert into tasks[] registry for worktree-manager
• releaseTask(taskId, projectPath) - atomic removal from tasks[] registry for ship/abort; idempotent