multi_agent_chat/permissions: surface MCP tool metadata into ask interrupts

The FE permission card needs mcp_connector_id, mcp_server, and
tool_description in the interrupt context to render "Always Allow"
against the right connected account. Thread the tool through the
ask pipeline:

- pack_subagent → build_permission_mw(tools=...) → PermissionMiddleware
  (tools_by_name) → request_permission_decision(tool=...) →
  build_permission_ask_payload(tool=...) projects card fields out of
  BaseTool.

- mcp_tool.py: stdio path now stashes mcp_connector_id in metadata for
  parity with the HTTP path.

surfsense_backend/app/agents/new_chat/tools/mcp_tool.py

@@ -229,6 +229,7 @@ async def _create_mcp_tool_from_definition_stdio(
             "mcp_input_schema": input_schema,
             "mcp_transport": "stdio",
             "mcp_connector_name": connector_name or None,
+            "mcp_connector_id": connector_id,
             "mcp_is_generic": True,
             "hitl": True,
             # Full-args hash: shared identifiers (cloudId, workspaceId, …)