src/search/ranking.py computed result age as `(datetime.now() - dt).days`, where
`dt` is parsed from a UTC-style published date with no timezone. Using local
`datetime.now()` skewed the age by the host's UTC offset (off-by-up-to-a-day near
boundaries), and was a latent crash: once neighbouring code becomes timezone-aware
the naive/aware subtraction raises TypeError (the landmine called out in #1116).
Recency is now measured against naive UTC. The scoring is also lifted out of the
rank_search_results closure into a module-level, time-injectable `recency_score`
so it's unit-testable, and `_utcnow_naive()` avoids `datetime.utcnow()` (removed in
Python 3.14).
Covered by tests/test_search_ranking_recency.py (5 cases); the existing
tests/test_search_ranking.py still passes.
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
