backup-whey-to-ssd.sh: ledger success field does not cover teardown/release_mount outcome

Run ledger recorded status=success with finished_at set for run #270 even though the EXIT-trap teardown (release_mount) crashed and never ran (v2.1 was overwritten in-place mid-run, desyncing bash's byte offset, exit 127). The backup body succeeded and wrote its own ledger row before the trap fired, so a trap/teardown failure is invisible to the ledger success field. Either teardown becomes its own recorded outcome, or 'success' is documented as body-only (never implying cleanup ran). See memory/reference_luks_stale_crypt_mapping.md for full detail. Filed per pmmaster ruling 2026-09-12.