feat(sdks): add parsers[].pageMarkers for PDF page attribution (#4379)

Expose the v2 PDF parser pageMarkers option across the JS, Python, Go,
Java, Ruby, PHP, Rust, and .NET SDKs so scrape/parse requests can join
PDF pages in document.markdown with <!-- page N --> separators. Bump
each package version so merge auto-publishes.

Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: Abimael Martell <abimaelmartell@users.noreply.github.com>