test(node-integration): Retry RabbitMQ connect in amqplib scenario (#21062)

## Summary

- Wraps `connectToRabbitMQ()` in `suites/tracing/amqplib/scenario.mjs`
with a 5-attempt, 1-second-backoff retry loop. First attempt is
unchanged; only retries trigger on connect rejection.

## Root cause

From the [failing
run](https://github.com/getsentry/sentry-javascript/actions/runs/26030287555/job/76514895508):

```
FAIL suites/tracing/amqplib/test.ts > amqplib auto-instrumentation > esm/cjs > esm > should be able to send and receive messages
Error: Expected envelope item type 'transaction' but got 'event'.
Item: [{"type":"event"},{"exception":{"values":[{"type":"Error","value":"Socket closed abruptly during opening handshake", ...
```

The docker-compose healthcheck (`rabbitmq-diagnostics -q ping`) reports
the broker ready before its AMQP listener can complete the protocol
handshake. So:

1. Healthcheck passes → runner launches the scenario.
2. `await amqp.connect(AMQP_URL)` rejects with `Socket closed abruptly
during opening handshake`.
3. The rejection isn't caught by the top-level IIFE →
`OnUnhandledRejection` integration captures it → Sentry sends it as an
error envelope.
4. The runner's strict envelope-stream parser (`utils/runner.ts:509`)
sees an `event` where it expected a `transaction` and throws.

## Fix

Add a retry loop around `amqp.connect` + `createChannel`. The first
attempt path is unchanged (no extra latency in the common case). On
transient connection rejection, retry up to 4 more times with 1 s
spacing — total worst-case extra time 4 s, well within the test's 60 s
timeout. After 5 failures, throws `lastError` (same failure mode as
today, just delayed).

Connection retry is the industry-standard pattern for broker-readiness
races where the healthcheck reports a coarser signal than the actual
protocol. The change is purely additive — first-attempt success is
unchanged, assertions are unchanged, and a truly broken broker still
surfaces as a scenario failure.

Fixes #20969

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Author: mydea

dev-packages/node-integration-tests/suites/tracing/amqplib/scenario.mjs

@@ -35,9 +35,26 @@ const QUEUE_OPTIONS = {
 })();
 
 async function connectToRabbitMQ() {
-  const connection = await amqp.connect(AMQP_URL);
-  const channel = await connection.createChannel();
-  return { connection, channel };
+  // Retry up to 5 times with 1s backoff. The docker-compose healthcheck
+  // (`rabbitmq-diagnostics -q ping`) reports the broker ready before AMQP
+  // handshakes actually succeed, so the first connect can race with broker
+  // boot and reject with "Socket closed abruptly during opening handshake".
+  // That rejection becomes an unhandled rejection captured by Sentry and
+  // sent as an error envelope, which the runner sees ahead of the expected
+  // transaction and reports as "Expected envelope item type 'transaction'
+  // but got 'event'" (the flake reported in the issue).
+  let lastError;
+  for (let attempt = 0; attempt < 5; attempt++) {
+    try {
+      const connection = await amqp.connect(AMQP_URL);
+      const channel = await connection.createChannel();
+      return { connection, channel };
+    } catch (err) {
+      lastError = err;
+      await new Promise(resolve => setTimeout(resolve, 1000));
+    }
+  }
+  throw lastError;
 }
 
 async function createQueue(queueName, channel) {