The source plan's bulletin-history schema declared a four-value
status enum: success, network_error, parse_error,
validation_rejected. The poller only ever wrote the first three;
when PatchLevelManager.updateTo silently rejected a date for bad
format, floor violation, past/future bounds, or atomicWrite IO
error, the history still recorded status=success and applied=true
because applied was set from isNewer before updateTo ran.
Make updateTo return Boolean. Wire the result through fetchAndParse
so a rejected apply lands as status=validation_rejected with
applied=false and an error string identifying the date that failed.
Closes the only spec gap from fancy-humming-firefly.md uncovered
during the source-plan cross-audit.