allow multiple tool calls, log warnings if there are duplicate calls.

controlled via a flag to the agent config:
allow_multiple_tool_calls = true

crates/g3-config/tests/test_multiple_tool_calls.rs

@@ -0,0 +1,39 @@
+#[cfg(test)]
+mod test_multiple_tool_calls {
+    use g3_config::{Config, AgentConfig};
+    
+    #[test]
+    fn test_config_has_multiple_tool_calls_field() {
+        let config = Config::default();
+        
+        // Test that the field exists and defaults to false
+        assert_eq!(config.agent.allow_multiple_tool_calls, false);
+        
+        // Test that we can create a config with the field set to true
+        let mut custom_config = Config::default();
+        custom_config.agent.allow_multiple_tool_calls = true;
+        assert_eq!(custom_config.agent.allow_multiple_tool_calls, true);
+    }
+    
+    #[test]
+    fn test_agent_config_serialization() {
+        let agent_config = AgentConfig {
+            max_context_length: Some(100000),
+            fallback_default_max_tokens: 8192,
+            enable_streaming: true,
+            allow_multiple_tool_calls: true,
+            timeout_seconds: 60,
+            auto_compact: true,
+            max_retry_attempts: 3,
+            autonomous_max_retry_attempts: 6,
+        };
+        
+        // Test serialization
+        let json = serde_json::to_string(&agent_config).unwrap();
+        assert!(json.contains("\"allow_multiple_tool_calls\":true"));
+        
+        // Test deserialization
+        let deserialized: AgentConfig = serde_json::from_str(&json).unwrap();
+        assert_eq!(deserialized.allow_multiple_tool_calls, true);
+    }
+}