[fix] resolve 16 mypy errors across 9 test files (make quality gate)

type-clean the test files so make quality (mypy roboco/ tests/) is green:
- Any-typed locals for the two TypeError-asserting scoping tests (bypass
  the required-arg check without getattr/ruff B009)
- Any-typed view for the shutdown-drain _drain_bg_tasks override (bypass
  mypy method-assign without setattr/ruff B010)
- cast("uuid.UUID", ...) / cast("UUID", ...) for SQLAlchemy UUID[Any]
  returns (TC006-quoted), config=None for AgentInstance stubs, None-narrowed
  await_args, Iterator return on a yielding fixture, UUID annotation on the
  _task helper. No type:ignore / noqa.

tests/integration/test_notification_delivery_phantom.py

@@ -8,7 +8,7 @@ SQLAlchemy ``after_commit`` events and a recording bus stand-in.
 from __future__ import annotations
 
 import asyncio
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, cast
 from uuid import UUID, uuid4
 
 import pytest
@@ -99,7 +99,7 @@ async def _seed_agents_and_notification(
             metrics={},
         )
         db.add(r)
-        recipient_ids.append(r.id)
+        recipient_ids.append(cast("UUID", r.id))
     await db.flush()
 
     notification = NotificationTable(
@@ -113,7 +113,7 @@ async def _seed_agents_and_notification(
     )
     db.add(notification)
     await db.flush()
-    return notification.id, notification
+    return cast("UUID", notification.id), notification
 
 
 @pytest.mark.asyncio