chore: apply ruff auto-fixes and remove dead AST scripts

aggregate.py

@@ -256,7 +256,7 @@ def build_tier3_context(file_items: list[dict[str, Any]], screenshot_base_dir: P
       parser = ASTParser("python")
       skeleton = parser.get_skeleton(content)
       sections.append(f"### `{entry or path_str}` (AST Skeleton)\n\n```python\n{skeleton}\n```")
-     except Exception as e:
+     except Exception:
      # Fallback to summary if AST parsing fails
       sections.append(f"### `{entry or path_str}`\n\n" + summarize.summarise_file(path, content))
     else: