- ensure_workers_table: new tables include host TEXT, pid BIGINT,
address TEXT; old tables gain them via _ensure_hostpid_columns
(PRAGMA column check, missing-only ALTER, old rows keep NULL,
never fabricates host/pid). SQLite and Postgres share this path
(PG via the db adapter's PRAGMA translation); POSTGRES_SCHEMA
deliberately still excludes workers, which is volatile heartbeat
data in UNMIGRATED_TABLES (adding it broke the P2 migration
alignment tests, verified and reverted).
- heartbeat/register: given host/pid/address refresh, omitted
values preserve the old row; address has no derived source.
Local worker passes host_name + own pid; HTTP heartbeat only
stores caller-supplied values, never the server's own.
- classify_stale_workers: kill only when age strictly exceeds the
threshold AND host matches local host AND pid is proven dead;
equal threshold, foreign host, missing pid, or live/unknown pid
are list_only. Classification only, never kills, never matches
by name/prefix, never touches infra containers.
