[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/unit/runtime/test_secretary_spawn_shutdown.py

@@ -9,7 +9,7 @@ from __future__ import annotations
 import asyncio
 from pathlib import Path
 from types import SimpleNamespace
-from typing import Any
+from typing import TYPE_CHECKING, Any
 from unittest.mock import patch
 from uuid import UUID
 
@@ -20,6 +20,9 @@ from roboco.runtime.orchestrator import (
 )
 from roboco.services import prompter_live
 
+if TYPE_CHECKING:
+    from collections.abc import Iterator
+
 
 def _make_orchestrator() -> AgentOrchestrator:
     """AgentOrchestrator with constructor I/O skipped; a RUNNING minimal one."""
@@ -97,7 +100,7 @@ def _wire_secretary_spawn_mocks(
 
 
 @pytest.fixture(autouse=True)
-def _fresh_registry() -> None:
+def _fresh_registry() -> Iterator[None]:
     """Isolate the process-wide live registry per test."""
     prev = prompter_live._RegistryHolder.instance
     prompter_live._RegistryHolder.instance = prompter_live.PrompterLiveRegistry()