purge_stale_tool_call_markers ran a permanent, irreversible UPDATE with
no backup — inconsistent with repair_state_db_schema's backup-by-default
convention for destructive state.db operations elsewhere in this file.
Take a full snapshot via VACUUM INTO (safe against a live connection,
unlike the raw-copy _backup_db_file used for malformed-schema repair)
before the write, timestamped beside state.db. Skipped when dry_run or
when there's nothing to change. Add --no-backup to `hermes sessions
clean-markers`, mirroring `sessions repair`.
Verified end-to-end: the CLI run against a real temp state.db produces
the backup file before printing the cleared-row count.
The load-on-read repair (_strip_stale_tool_call_markers) fixes affected
sessions in memory on every resume, but never touches the DB — long-lived
sessions re-scan and re-repair the same rows on every load, and the
contaminated bytes stay in state.db (and any backup/cache snapshot of it)
indefinitely.
Add SessionDB.purge_stale_tool_call_markers(dry_run=False): a one-time,
idempotent UPDATE that permanently blanks the content column on affected
rows. Only content is touched — tool_calls and every other column are
left untouched, so provider tool_call/tool_result pairing survives.
dry_run reads through the no-lock read path and never writes.
Wire it up as `hermes sessions clean-markers [--dry-run]`, mirroring the
existing optimize/repair subcommands. Verified end-to-end against a real
temp state.db: dry-run reports the row without writing, the real run
clears it and preserves tool_calls, and a second run is a no-op.