fix: handle dict tool call arguments from local backends

Normalize tool call arguments when OpenAI-compatible backends return parsed dict/list payloads instead of JSON strings. This prevents the .strip() crash during tool-call validation for llama.cpp and similar servers, while preserving existing empty-string and invalid-JSON handling. Adds a focused regression test for dict arguments in the agent loop.

run_agent.py

@@ -5582,6 +5582,12 @@ class AIAgent:
                     invalid_json_args = []
                     for tc in assistant_message.tool_calls:
                         args = tc.function.arguments
+                        if isinstance(args, (dict, list)):
+                            tc.function.arguments = json.dumps(args)
+                            continue
+                        if args is not None and not isinstance(args, str):
+                            tc.function.arguments = str(args)
+                            args = tc.function.arguments
                         # Treat empty/whitespace strings as empty object
                         if not args or not args.strip():
                             tc.function.arguments = "{}"