chore: regression test for KV panic on uncaught error with listenQueue (#34553)

## Summary

Locks in the fix for
[#20464](#20464):
opening a KV, attaching `listenQueue()` without `await`, and then
hitting an uncaught error on the main task used to panic the runtime
with `Attempted to use a closed database` (at `ext/kv/sqlite.rs:440` in
1.36.4) while the queue's dequeue loop raced against the dropped SQLite
connection.

The 2023 reporter triggered it from Fresh's `dev.ts` (a `ReferenceError:
Cannot access 'manifest' before initialization` followed by `await
start(manifest, config)`), but the underlying race was generic to any
uncaught error on the main task while `listenQueue` was outstanding. The
runtime now unwinds cleanly: the JS error surfaces, the process exits
non-zero, and there is no panic. This spec test pins that behavior so
the property isn't lost silently if the queue/close ordering is
refactored again.

The new spec mirrors the reporter's setup: open
`Deno.openKv(":memory:")`, fire `kv.listenQueue(() => {})` without
`await`, log `Listening for messages...`, then `throw new Error(...)`.
The test asserts exit code 1 and the JS error in stderr — any future
regression that brings back the panic would change exit status and add a
`Deno has panicked` block to the output.

## Test plan

- [x] `target/debug/deps/specs-* kv_listen_queue_uncaught_error` passes
locally
- [x] Verified `deno run --watch` against the same reproducer prints the
JS error and waits for a file change with no panic / no backtrace

Closes denoland/orchid#299

Co-authored-by: divybot <divybot@users.noreply.github.com>
Co-authored-by: Divy Srivastava <me@littledivy.com>

Author: divybot

tests/specs/run/kv_listen_queue_uncaught_error/__test__.jsonc

@@ -0,0 +1,6 @@
+{
+  "tempDir": true,
+  "args": "run -A --unstable-kv main.ts",
+  "exitCode": 1,
+  "output": "main.out"
+}

tests/specs/run/kv_listen_queue_uncaught_error/main.out

@@ -0,0 +1,3 @@
+Listening for messages...
+error: Uncaught (in promise) Error: kaboom from main
+[WILDCARD]

tests/specs/run/kv_listen_queue_uncaught_error/main.ts

@@ -0,0 +1,16 @@
+// Copyright 2018-2026 the Deno authors. MIT license.
+
+// Regression test for https://github.com/denoland/deno/issues/20464
+// Opening a KV, attaching listenQueue() without await, and then hitting an
+// uncaught error on the main task used to panic the runtime with
+// "Attempted to use a closed database" while the queue's dequeue loop raced
+// against the dropped SQLite connection. The error path must now unwind
+// cleanly: surface the JS error, exit non-zero, no panic.
+
+const kv = await Deno.openKv(":memory:");
+kv.listenQueue(() => {});
+console.log("Listening for messages...");
+
+// Mirror the reporter's "Cannot access 'manifest' before initialization"
+// — any uncaught error on the main task is enough to expose the race.
+throw new Error("kaboom from main");