Fix send_command return type annotation to include MCPResponse

The send_command method can return either dict[str, Any] or MCPResponse,
but the return type annotation only declared dict[str, Any]. This causes
type-checking inconsistencies when the method returns MCPResponse on
line 279-284 (when Unity is reloading).

Changes:
- Update return type from `-> dict[str, Any]` to `-> dict[str, Any] | MCPResponse`
- Applied to both Server/ and MCPForUnity/ versions
- Ensures static type checkers recognize MCPResponse as valid return value

Addresses CodeRabbit feedback:
- #360 (comment)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: sakurachan

MCPForUnity/UnityMcpServer~/src/unity_connection.py

@@ -225,7 +225,7 @@ def receive_full_response(self, sock, buffer_size=config.buffer_size) -> bytes:
             logger.error(f"Error during receive: {str(e)}")
             raise
 
-    def send_command(self, command_type: str, params: dict[str, Any] | None = None) -> dict[str, Any]:
+    def send_command(self, command_type: str, params: dict[str, Any] | None = None) -> dict[str, Any] | MCPResponse:
         """Send a command with retry/backoff and port rediscovery. Pings only when requested."""
         # Defensive guard: catch empty/placeholder invocations early
         if not command_type:

Server/unity_connection.py

@@ -225,7 +225,7 @@ def receive_full_response(self, sock, buffer_size=config.buffer_size) -> bytes:
             logger.error(f"Error during receive: {str(e)}")
             raise
 
-    def send_command(self, command_type: str, params: dict[str, Any] | None = None) -> dict[str, Any]:
+    def send_command(self, command_type: str, params: dict[str, Any] | None = None) -> dict[str, Any] | MCPResponse:
         """Send a command with retry/backoff and port rediscovery. Pings only when requested."""
         # Defensive guard: catch empty/placeholder invocations early
         if not command_type: