chore(post-audit): document notify verb + remove # type: ignore

Audit followups before pushing the gateway-restoration batch:
- Add notify() row to cell_pm.md, main_pm.md, board.md verb tables.
  Manifests + routes + MCP + tests all wired in 3a2498a but agents
  had no prompt-level cue.
- Replace # type: ignore[attr-defined] in test_pm_respawn_reset.py
  with cast('Any', orch) — matches project's no-suppress standard.

tests/unit/runtime/test_pm_respawn_reset.py

@@ -23,6 +23,7 @@ instead of incrementing.
 from __future__ import annotations
 
 from datetime import UTC, datetime
+from typing import Any, cast
 from unittest.mock import AsyncMock, patch
 from uuid import uuid4
 
@@ -34,7 +35,7 @@ from roboco.seeds.initial_data import AGENT_UUIDS
 def _new_orchestrator() -> AgentOrchestrator:
     """Bypass __init__ so tests don't need a full DI graph."""
     orch = AgentOrchestrator.__new__(AgentOrchestrator)
-    orch._pm_respawn_tracker = {}  # type: ignore[attr-defined]
+    cast("Any", orch)._pm_respawn_tracker = {}
     return orch