UAT found and resolved a concatenation collision in _compute_fgp (no separator
between user_agent and accept_lang). Fix committed in c77b97b. All 5 FGP tests
pass. Full suite: 401 passed, 6 skipped, 7 xfailed, 1 pre-existing failure
(test_extract_docx — missing docx module, unrelated to this phase).
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>