fix(ai-markmap-agent): fix save_all_markmaps return and resume functionality

- Add missing `return saved_files` in save_all_markmaps function
  (was causing 'NoneType' has no len() error)
- Pass _resume_config from data dict to initial_state in run_pipeline
  and run_pipeline_async
- Add _resume_config to WorkflowState TypedDict to ensure LangGraph
  preserves it across all graph nodes (root cause of resume not working)

Author: lufftw

tools/ai-markmap-agent/src/graph.py

@@ -93,6 +93,9 @@ class WorkflowState(TypedDict, total=False):
     # Metadata
     messages: list[str]
     errors: list[str]
+    
+    # Resume configuration (internal)
+    _resume_config: dict[str, Any]
 
 
 def load_baseline_markmap(config: dict[str, Any]) -> str: