Merge fix/ADFA-5039 into fix/ADFA-4739 (md_to_json.py review fixes)

Brings this branch's copy of md_to_json.py up to PR #23's tip. It had been
stale since the 1cf41d2 merge: 4fddb34 ("Fix 10 issues from Hal's automated
corpus review") and 1d7f6a7 ("Fix 6 latent defects from the md_to_json.py code
review") both landed on fix/ADFA-5039 afterwards, and populate_db.py,
build_nav.py and find_missing_assets.py all import this module directly.

md_to_json.py and tests/test_md_to_json.py are now identical on both branches.

One conflict, in requirements.txt, resolved as the union: this branch added
scour/cairosvg for optimize_media.py, #23 pinned markdown-it-py>=2.0.

158 tests pass (131 in ProcessKotlinWebsiteJSON, 27 in sync_kotlin_stdlib_docs).

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: 2 people