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/src/beads_mcp/mail_tools.py

@@ -155,7 +155,7 @@ def beads_mail_reply(params: MailReplyParams) -> dict[str, Any]:
         return {"error": e.code, "message": e.message, "data": e.data}
 
 
-def beads_mail_ack(params: MailAckParams) -> dict[str, bool]:
+def beads_mail_ack(params: MailAckParams) -> dict[str, Any]:
     """Acknowledge a message (for ack_required messages).
 
     Safe to call even if message doesn't require acknowledgement.
@@ -183,7 +183,7 @@ def beads_mail_ack(params: MailAckParams) -> dict[str, bool]:
         return {"error": e.code, "acknowledged": False, "message": e.message}
 
 
-def beads_mail_delete(params: MailDeleteParams) -> dict[str, bool]:
+def beads_mail_delete(params: MailDeleteParams) -> dict[str, Any]:
     """Delete (archive) a message from Agent Mail inbox.
 
     Note: Agent Mail archives messages rather than permanently deleting them.