sqlite: the listen bridge takes the stream bridge's std-thread shape (review 004 item 8) — one dedicated named thread per subscription doing blocking_send, not a spawn_blocking task (past ~500 listeners the blocking-pool ceiling queued the whole engine's seams); spawn failure unsubscribes and fails closed with Error::Database, matching the stream bridge's posture; notify.rs + engine-sqlite.md docs aligned; task -> completed

docs/architecture/engine-sqlite.md

@@ -79,7 +79,7 @@ per-contract obligations live in the core spec and are not restated here.
 
 | Contract piece | Engine realization |
 |---|---|
-| notify / listen | honker's notify functions inside the caller's tx; `listen()` bridges the watcher's fanout into a tokio receiver (one `spawn_blocking` thread per subscription doing `blocking_send`) |
+| notify / listen | honker's notify functions inside the caller's tx; `listen()` bridges the watcher's fanout into a tokio receiver (one dedicated `std::thread` per subscription doing `blocking_send` — the stream bridge's aligned shape, review 004 item 8; the same thread is not a `spawn_blocking` task, so parked bridges never consume the blocking pool the engine's seams share) |
 | streams | the forked substrate's stream machinery (inherited near-verbatim — the `__alkstore_stream` table's field set is already the contract's shape (its `topic` column carries the contract's `stream` field — the one name delta, ADR-012 §3's fidelity posture), the offset-ASC read path, keyed publish's nullable key column, monotone offset saves ([ADR-015](decisions/015-streams-depth.md)); explicit offset saves through the tx seam; `trim_to` is a `DELETE FROM … WHERE offset <= ?` inside the writer-slot lease) |
 | queues | owned queue machinery (forked substrate re-derived on [ADR-010](decisions/010-queue-semantics-depth.md) — stamps, no-stranded-rows sweep, dead-visible `get_job`); ADR-003's ride posture superseded on ownership by [ADR-011](decisions/011-sqlite-substrate-fork.md) |
 | named locks | the substrate's lock machinery (`lock_renew` carries the renew semantics the guarantee row pins; re-acquire does not refresh TTL — inherited deliberately, [ADR-012](decisions/012-forked-substrate-design.md) §4) |