feat: first-class control-plane lease lifecycle (Closes #601)

Make active leases queryable workflow state with canonical adopt, release,
expire/reclaim, and abandon operations on the #613 control-plane DB substrate.

- lease_lifecycle.py: policy, proof gates, safe_next_action vocabulary
- control_plane_db: schema v3 provenance columns + list/inspect/adopt/abandon
- MCP tools: gitea_*_workflow_lease(s) for list/inspect/adopt/release/expire/abandon/reclaim
- issue_lock_store: sanctioned reclaim of expired author locks (dead pid / missing wt)
- Tests cover lifecycle, foreign steal refusal, allocator compatibility, merger handoff

docs/architecture/control-plane-db-substrate.md

@@ -51,6 +51,35 @@ Module: `allocator_service.py` · MCP tool: `gitea_allocate_next_work`
 - Routing follows ADR §5.3 (REQUEST_CHANGES → author, terminal path first, foreign lease → wait).
 - Raw monitoring incidents are never candidates.
 
+
+## Lease lifecycle API (#601)
+
+Module: `lease_lifecycle.py` · MCP tools: `gitea_*_workflow_lease(s)`
+
+Active control-plane leases are **first-class workflow state**:
+
+| Tool | Purpose |
+|------|---------|
+| `gitea_list_workflow_leases` | List active (or all) leases for a repo |
+| `gitea_inspect_workflow_lease` | Freshness + `safe_next_action` for one lease id |
+| `gitea_adopt_workflow_lease` | Owner-resume or sanctioned reclaim with provenance |
+| `gitea_release_workflow_lease` | Explicit owner release (audited) |
+| `gitea_expire_workflow_leases` | Deterministic expire of past-`expires_at` leases |
+| `gitea_abandon_workflow_lease` | Abandon with required proof |
+| `gitea_reclaim_expired_workflow_lease` | Expire + re-assign with provenance |
+
+### Hard rules
+
+1. Control-plane DB is the coordination authority — file locks / comment-only leases are not authoritative alone.
+2. Active foreign leases cannot be stolen; inspect returns `wait_foreign_active`.
+3. Abandon requires `(dead_process OR missing_worktree)` and `no_live_mutation_risk`; foreign abandon also needs `operator_authorized` or full dead+missing+no_open_pr proof.
+4. Adopt provenance always records `adopted_from_session_id`, `adopted_by_session_id`, work identity, optional head SHA, and worktree path.
+5. Reviewer→merger comment handoff (`gitea_adopt_merger_pr_lease`) is unchanged and remains the Gitea-thread durability path.
+
+```bash
+python3 -m pytest tests/test_lease_lifecycle.py tests/test_control_plane_db.py tests/test_allocator_service.py tests/test_merger_lease_adoption.py -q
+```
+
 ## Incident bridge (#612)
 
 Module: `incident_bridge.py` · MCP tools: `gitea_observability_*`