Fix type annotation inconsistency in negotiate() method

- Update multiselect.py negotiate() return type to match IMultiselectMuxer interface
- Allow TProtocol to be None in return type annotation
- Add .tmp.driveupload/ to .gitignore to exclude temporary upload files

Resolves type inconsistency between abstract interface and concrete implementation.

Author: keval215

.gitignore

@@ -178,3 +178,6 @@ env.bak/
 #lockfiles
 uv.lock
 poetry.lock
+
+# Temporary upload files
+.tmp.driveupload/

libp2p/protocol_muxer/multiselect.py

@@ -48,12 +48,11 @@ def add_handler(
         """
         self.handlers[protocol] = handler
 
-    # FIXME: Make TProtocol Optional[TProtocol] to keep types consistent
     async def negotiate(
         self,
         communicator: IMultiselectCommunicator,
         negotiate_timeout: int = DEFAULT_NEGOTIATE_TIMEOUT,
-    ) -> tuple[TProtocol, StreamHandlerFn | None]:
+    ) -> tuple[TProtocol | None, StreamHandlerFn | None]:
         """
         Negotiate performs protocol selection.