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>

docs/architecture/README.md

@@ -585,7 +585,7 @@ sentinel-state, `write_post_deploy_log`.
 Подробнее: [adr-0010](adr/adr-0010-post-deploy-monitor.md), детально —
 `docs/work-items/ORCH-021/06-adr/ADR-001-post-deploy-monitor.md`.
 
-### Terminal-window-aware гард deploy-статусов: done-задача держит Done (ORCH-094 — design)
+### Terminal-window-aware гард deploy-статусов: done-задача держит Done (ORCH-094 — реализовано)
 Терминальная (`done`) задача в Plane **не держала `Done`**: непрерывный флапп
 `Awaiting Deploy ⟷ Monitoring after Deploy` (верифицировано на **ORCH-061**, task 47, done с 07.06 —
 273 активности, само не затихает). Причина: три code-писателя deploy-фазовых статусов