fix: return capabilities.tools as object in MCP initialize response

[springfall2008]

Summary

Fixes #3496

The MCP initialize response was returning capabilities.tools as an array of tool objects (the result of tools/list) instead of an empty object {} as required by the MCP specification.

Strict MCP clients (e.g. Claude Desktop via mcp-remote using @modelcontextprotocol/sdk) validate against the spec and fail immediately with:

Connection error: $ZodError: [
  {
    "expected": "object",
    "code": "invalid_type",
    "path": ["capabilities", "tools"],
    "message": "Invalid input: expected object, received array"
  }
]

Fix

In _handle_initialize, removed the call to _handle_tools_list() and changed capabilities.tools to an empty object {}:

# Before
async def _handle_initialize(self, params):
    tools = await self._handle_tools_list(params)
    return {"protocolVersion": "2024-11-05", "capabilities": {"tools": tools["tools"]}, ...}

# After
async def _handle_initialize(self, params):
    return {"protocolVersion": "2024-11-05", "capabilities": {"tools": {}}, ...}

The tool list is correctly returned in response to tools/list requests — it does not belong in the initialize capabilities field.