Improve type safety and fix minor issues in beads-mcp

Type Safety Improvements:
- Change dict → dict[str, Any] throughout codebase for explicit typing
- Add PEP 561 py.typed marker file to export type information
- Add types-requests to dev dependencies
- Improve signal handler typing (FrameType | None)
- Improve decorator typing (Callable[..., Awaitable[T]])
- Add quickstart() abstract method to BdClientBase for interface completeness

Bug Fixes:
- Fix variable shadowing: beads_dir → local_beads_dir in bd_client.py
- Improve error handling in mail.py:_call_agent_mail() to prevent undefined error
- Make working_dir required (not Optional) in BdDaemonClient
- Remove unnecessary 'or' defaults for required Pydantic fields

Validation:
- mypy passes with no errors
- All unit tests passing
- Daemon quickstart returns helpful static text (RPC doesn't support this command)

integrations/beads-mcp/pyproject.toml

@@ -89,4 +89,5 @@ dev = [
     "pytest-asyncio>=1.2.0",
     "pytest-cov>=7.0.0",
     "ruff>=0.14.0",
+    "types-requests>=2.31.0",
 ]