fix(python): use 'is not None' check for excluded_tools in session methods (#596)

Fix truthy check for excluded_tools in create_session and resume_session
that silently dropped empty lists ([]), preventing callers from explicitly
clearing excluded tools.

This is the remaining half of #487 — available_tools was already fixed.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: patniko

python/copilot/client.py

@@ -497,7 +497,7 @@ async def create_session(self, config: SessionConfig) -> CopilotSession:
         if available_tools is not None:
             payload["availableTools"] = available_tools
         excluded_tools = cfg.get("excluded_tools")
-        if excluded_tools:
+        if excluded_tools is not None:
             payload["excludedTools"] = excluded_tools
 
         # Always enable permission request callback (deny by default if no handler provided)
@@ -675,7 +675,7 @@ async def resume_session(self, session_id: str, config: ResumeSessionConfig) ->
             payload["availableTools"] = available_tools
 
         excluded_tools = cfg.get("excluded_tools")
-        if excluded_tools:
+        if excluded_tools is not None:
             payload["excludedTools"] = excluded_tools
 
         provider = cfg.get("provider")