feat(kb_workflow): add archive_file to process_command return value

- Extract archive_file from pipeline results and include in response
- Allows callers to get the final archive path instead of only content_dir
- Fixes report display issue where content directory showed working dir instead of archive location

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

kb_workflow/kb_workflow.py

@@ -80,10 +80,16 @@ def process_command(
         # Run async pipeline
         result = asyncio.run(run_pipeline())
 
+        # Extract archive_file from results if available
+        archive_file = None
+        if result.results and "archive" in result.results:
+            archive_file = result.results["archive"].get("archive_file")
+
         return {
             "success": result.success,
             "error": result.error_message,
             "content_dir": str(result.content_dir) if result.content_dir else None,
+            "archive_file": archive_file,
             "results": result.results,
         }