fix(notion-writer): use module-level sys instead of inline import in toggle warning

Code review caught a redundant `import sys as _sys` inside the unclosed-
<details> branch. The module already imports `sys` at the top, so the
inline import was dead weight. Use the module-level `sys.stderr` directly.

26/26 tests still pass.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

custom-skills/32-notion-writer/code/scripts/notion_writer.py

@@ -123,9 +123,8 @@ def _parse_lines(lines: List[str]) -> List[Dict[str, Any]]:
                 i += 1
             if depth > 0:
                 # Unclosed <details> at EOF — degrade to paragraphs
-                import sys as _sys
                 print("Warning: unclosed <details> at EOF; emitting body as paragraphs",
-                      file=_sys.stderr)
+                      file=sys.stderr)
                 if summary_text:
                     blocks.append(create_paragraph_block(summary_text))
                 for inner in inner_lines: