added nullable ?: break support with proper inference ;)

docs/ai_notes_docs_headings.md

@@ -0,0 +1,10 @@
+# AI notes: heading levels must be consecutive
+
+[//]: # (excludeFromIndex)
+
+When editing repository documentation:
+
+- Use heading levels in order: `#`, then `##`, then `###`, and so on.
+- Do not skip levels, for example `#` directly to `###`.
+- Keep the heading tree balanced inside each document; sibling sections should use the same level.
+- If you add a subsection and the parent is `##`, the child must be `###`.