fix(deploy): terminal-window-aware guard so done tasks hold Done in Plane (ORCH-094)

A DB stage=done task with 0 active jobs flapped in Plane between `Awaiting
Deploy` and `Monitoring after Deploy` instead of holding `Done` (verified live
on ORCH-061, task 47): the three deploy-phase setters were terminal-blind, so
any stale/duplicate/unknown caller under the bot token re-stamped an
intermediate status over the terminal Done, forever.

- New leaf src/deploy_status_guard.py (pure, never-raise, config-gated): decide()
  -> ALLOW | CONVERGE_DONE | SUPPRESS on the entry of set_issue_awaiting_deploy /
  set_issue_deploying / set_issue_monitoring. A deploy-phase status is legitimate
  iff the task is non-terminal OR (done AND post-deploy window active); otherwise
  done converges to Done idempotently, cancelled is suppressed (FR-2, D1/D2).
- D3: move post_deploy.arm_monitor ABOVE the terminal-sync block in advance_stage
  so window_active is True when the legitimate first Monitoring is set (the task
  is already DB-done by then); a re-drive after the window closes converges to Done.
- D4: run_post_deploy_monitor no-ops without a status PATCH / re-queue when the
  task became cancelled mid-window (zombie-tick guard, FR-3).
- D5: additive `reason` kwarg on the three setters + one structured log line per
  verdict (work_item/caller/target/db_stage/window_active/verdict); new read-only
  db.get_task_by_work_item_id; post_deploy.window_active helper.
- Flags deploy_status_guard_enabled (kill-switch -> 1:1) / deploy_status_guard_repos
  (CSV; empty = self-hosting only). STAGE_TRANSITIONS / QG_CHECKS / check_* /
  machine-verdict keys / DB schema untouched (reads existing tasks.stage).

Tests: TC-01..TC-12 across 5 new test modules + config flags; updated the
reason-kwarg assertions in test_deploy_terminal_sync / test_deploy_approve.
Full regress green (1413). Docs: CHANGELOG, CLAUDE.md, docs/architecture/README.md
(status -> реализовано), .env.example.

Refs: ORCH-094

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/db.py

@@ -223,6 +223,28 @@ def get_task_by_plane_id(plane_id: str) -> dict | None:
     return None
 
 
+def get_task_by_work_item_id(work_item_id: str) -> dict | None:
+    """ORCH-094: read-only lookup of the live task row by human-readable
+    ``work_item_id`` (e.g. ``"ORCH-061"``).
+
+    ``get_task_by_plane_id`` matches the Plane UUIDs (``plane_id`` /
+    ``plane_issue_id``), not the human-readable ``work_item_id`` the deploy-phase
+    setters receive — hence this thin accessor. A live row matches exactly; the
+    ORCH-090 cancel tombstones carry a ``#cancelled-<id>`` suffix on
+    ``work_item_id`` so they never collide with a clean id. No schema change.
+    """
+    if not work_item_id:
+        return None
+    conn = get_db()
+    try:
+        row = conn.execute(
+            "SELECT * FROM tasks WHERE work_item_id = ?", (work_item_id,)
+        ).fetchone()
+    finally:
+        conn.close()
+    return dict(row) if row else None
+
+
 def get_task_by_repo_branch(repo: str, branch: str) -> dict | None:
     """Find task by repo and branch name."""
     conn = get_db()