chore(conductor): Mark track 'MMA Core Engine Implementation' as complete and verify with Phase 6 tests

ai_client.py

@@ -679,7 +679,8 @@ def _send_gemini(md_content: str, user_message: str, base_dir: str,
         # Only stable content (files + screenshots) goes in the cached system instruction.
         # Discussion history is sent as conversation messages so the cache isn't invalidated every turn.
         sys_instr = f"{_get_combined_system_prompt()}\n\n<context>\n{md_content}\n</context>"
-        tools_decl = [_gemini_tool_declaration()]
+        td = _gemini_tool_declaration()
+        tools_decl = [td] if td else None
 
         # DYNAMIC CONTEXT: Check if files/context changed mid-session
         current_md_hash = hashlib.md5(md_content.encode()).hexdigest()