Round-1 review follow-ups (PR #879):
- Gate pages_embedded on `page_count and page_count > 0` so a malformed
negative count meters as "no pages" rather than emitting a negative
billing row (matches the documented call-site intent).
- Exclude bool at the call-site narrowing (`isinstance(int) and not
isinstance(bool)`) — bool is an int subclass, so a stray page_count=True
would otherwise record pages=1.
- Document chunk_count's role (empty-batch no-op guard) and the
intentional tokens-before-pages ordering in the docstring/comments.
- Add test_negative_pages_skips_pages.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
