format_session_db_unavailable consumes the now-pinned cause table but its own
two fallbacks (no recorded cause; network-drive gloss) still printed a bare
`hermes doctor`. Same class; one test covers both fallbacks.
Also: spell the corrupt action as plain concatenation instead of an f-string
with escaped braces, and fix the finalizer comment to state the invariant
(final_response is never rebound) rather than describe a local that no longer
exists.
532b6d1cb1