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

tasks/sqlite-fix-listener-bridge-alignment.md

@@ -1,7 +1,7 @@
 ---
 id: sqlite-fix-listener-bridge-alignment
 name: Align the sqlite listen bridge to the stream bridge's std-thread shape (review 004 item 8)
-status: pending
+status: completed
 depends_on: [sqlite-fix-watcher-death-subscribe]
 scope: narrow
 risk: low
@@ -53,6 +53,46 @@ stream bridge does.
 
 > To be filled by implementation agent
 
+Decisions of record the description didn't pin:
+
+- The two bridges' shapes are now exactly aligned: a named
+  `std::thread::Builder` thread (`alkstore-listen-bridge-{channel}`,
+  mirroring the stream bridge's `alkstore-stream-bridge-{stream}`), the
+  same loop body, and the stream bridge's spawn-failure posture — a
+  failed spawn unsubscribes the just-enrolled substrate feed and fails
+  closed with `Error::Database` (the stream bridge's W-2 no-panic-
+  across-the-seam shape). The spawn-failure arm is new here
+  (`spawn_blocking` was infallible at spawn); it matches the stream
+  bridge rather than being named as a residual difference.
+- Docs updated, not code-adjacent only: `notify.rs`'s module docs
+  (the bridge bullet + the `listen` entry-point doc now pin the
+  std-thread shape and the spawn-failure arm), and `engine-sqlite.md`'s
+  notify/listen mapping row (rewritten to the dedicated-thread shape
+  with the alignment reason). No PROVENANCE row: the register covers
+  `src/substrate/` only, and this change is engine-level (`notify.rs`).
+- No new test: the shape is not contract-observable at the receiver
+  surface (close semantics, wake delivery, no-replay all unchanged);
+  the existing pins cover the observable posture, including the
+  dead-watcher sign from the dependency task
+  (`listen_after_watcher_death_fails_closed` — green unchanged).
+
 ## Summary
 
-> To be filled on completion
+> To be filled on completion
+
+`listen()`'s watcher-fanout bridge now runs on a dedicated named
+`std::thread` instead of a tokio `spawn_blocking` task per
+subscription — the stream bridge's shape, eliminating the blocking-pool
+ceiling queueing (review 004 item 8); parked listen bridges no longer
+consume the shared blocking pool the engine's seams run on. Spawn
+failure fails closed (`Database` + unsubscribe), matching the stream
+bridge. Doc alignment: `notify.rs` module + entry-point docs,
+`engine-sqlite.md`'s mapping row.
+
+Verified: `cargo build`, `cargo test` (workspace, all green),
+`cargo test -p alkstore-sqlite` (201 + 25 tests, green — close
+semantics / wake delivery / no-replay pins and the dead-watcher-sign
+tests unchanged and passing), fuzz gate
+(`cargo test --manifest-path fuzz/shared/Cargo.toml`), clippy
+`-D warnings` clean, `cargo fmt --check` clean, rustdoc `-D warnings`
+doc gate clean.