Fix batch for Soul pass s1 (spec r3):
- Delete prune-on-absence and its test. Absence from Idunn's store no longer
deletes a journal entry, so an empty or restored store never re-sends.
- discord-dm exits 75 only when no message can have been sent (arguments,
token, DM channel open, non-2xx on the message POST). The reader records
failed for 75 only; any other non-success without a message id is unknown
and is never re-posted.
- Subject grammar is Idunn's require_id; the notice puts it in backticks.
- Times are bounded to the Date range; notice text is built before the
running entry is written.
Builds and passes on Linux. On Windows the two tests that SIGKILL the reader
cannot pass (process.kill does not deliver a signal there).
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>