docs(notion-writer): document mention pattern ordering and UUID format invariant

Code review flagged two implicit invariants worth pinning with comments:
- 'mention' must precede 'link' in INLINE_PATTERNS so the @[X](Y) prefix
  takes priority over plain link parsing
- format_id_with_dashes is required because the Notion mention API expects
  a dashed UUID while extract_notion_id returns dashless

32/32 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

@@ -277,7 +277,7 @@ def _parse_lines(lines: List[str]) -> List[Dict[str, Any]]:
 
 INLINE_PATTERNS = [
     ('code',          re.compile(r'`([^`\n]+)`')),
-    ('mention',       re.compile(r'@\[([^\]]+)\]\(([^)\s]+)\)')),
+    ('mention',       re.compile(r'@\[([^\]]+)\]\(([^)\s]+)\)')),  # must precede 'link' so @ takes priority
     ('link',          re.compile(r'\[([^\]]+)\]\(([^)\s]+)\)')),
     ('bold_star',     re.compile(r'\*\*([^*\n]+)\*\*')),
     ('bold_under',    re.compile(r'__([^_\n]+)__')),
@@ -352,6 +352,7 @@ def parse_rich_text(text: str) -> List[Dict[str, Any]]:
             mention_title, mention_target = m.group(1), m.group(2)
             page_id = extract_notion_id(mention_target)
             if page_id:
+                # Notion mention API requires dashed UUID; extract_notion_id returns dashless.
                 spans.append({
                     "type": "mention",
                     "mention": {