The gravity guard caught a correction that changed the gravity, but a
COMMENT-ONLY correction leaves the gravity unchanged - so the late
thread for the old advice still matched and overwrote the fresh one.
Reproduced against the live database:
fresh advice matched: 1
stale thread matched: 1 <-- should be 0
FINAL advice: 'STALE ADVICE'
Every edit now writes a fresh token onto the reading, and the advice
thread carries the token it was given. A late thread finds a token that
no longer matches, so its write is refused. The gravity is still
checked as well.
Verified against the live database:
token changed: True
fresh advice matched: 1
stale thread matched: 0 <-- must be 0
FINAL advice: 'FRESH ADVICE'
174 tests (up from 173).
hermes
a78aabe3ea