Fixes identified by comprehensive state machine validation:
- M12: reopen-task/slice now deletes SUMMARY.md from disk, preventing
the DB-filesystem reconciler from auto-correcting tasks back to
"complete" — reopen was previously a no-op when artifacts existed
- H4: add 30s hard timeout to unitPromise via Promise.race — prevents
permanent hang if supervision fails to resolve agent_end
- H5: add handleReopenMilestone — milestone completion was irrevocable
- H6: pass ID as title when auto-creating phantom parent entities
- H7: guard loadRegistry() against missing/corrupt registry.json
- M4: report_blocker replay now sets blocker_discovered flag via
new setTaskBlockerDiscovered() DB function
- M5: insertVerificationEvidence uses INSERT OR IGNORE with unique
index on (task_id, slice_id, milestone_id, command, verdict)
- M11: complete-slice rollback preserves original status instead of
hardcoding "pending"
- M14: deriveWorkflowAction shows contextual labels for blocked,
paused, validating-milestone, completing-milestone, needs-discussion,
and replanning-slice phases instead of generic "Continue"
Includes 86 regression tests (49 unit + 37 integration) validating
every phase transition, completion guard, and edge case.
Closes#3161
c6093b4bbd