Fix PostgreSQL recovery after a transaction connection closes (#13643)

Reject queued and late work from disconnected transaction and reservation
scopes. Keep closed reservations out of the open pool, and clear old
connection buffers and responses so new requests can reconnect safely.

Twelve real-PostgreSQL regression cases cover crash prevention, recovery,
and transaction isolation in both ESM and CommonJS. Database checks and
all PR CI checks pass. Greptile: 5/5, no unresolved comments.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

pnpm-workspace.yaml

@@ -16,6 +16,7 @@ packages:
 # Keep in sync with package.json#pnpm.patchedDependencies. Newer pnpm
 # versions read patch configuration only from the workspace manifest.
 patchedDependencies:
+  postgres@3.4.9: patches/postgres@3.4.9.patch
   embedded-postgres@18.1.0-beta.16: patches/embedded-postgres@18.1.0-beta.16.patch
   acpx@0.12.0: patches/acpx@0.12.0.patch
   acpx@0.13.1: patches/acpx@0.13.1.patch