Consumer::fetch()'s unsubscribe in finally can replace the exception it was added for

Consumer::fetch() moved its unsubscribe into a finally so the inbox subscription is not leaked on a throw (a real fix — attemptReconnect() re-subscribes every leaked sid, so the leak compounded across a reconnect storm):

// packages/nats/src/JetStream/Consumer.php:59
try {
    $this->conn->publish($requestSubject, $payload, $inbox);
    $this->collectBatch($sub, $messageBatch, $batch, $timeout);
} finally {
    $sub->unsubscribe();
}

Subscription::unsubscribe() reaches Connection::unsubscribe() → Connection::send(), which on a dead socket buffers, attempts a reconnect, and raises ConnectionException('Failed to reconnect to any NATS server') once attempts are exhausted.

In PHP an exception thrown from a finally replaces the one already in flight. So on the exact path the finally was added for — the connection died mid-fetch — the useful error (the -ERR, the JetStreamException, or the original ConnectionException naming what actually happened) is swapped for a generic reconnect failure. The subscription is still correctly cleaned up; only the diagnosis is lost, at the moment it matters most.

Fix: suppress a throw from unsubscribe() when an exception is already propagating — the connection is being torn down anyway, so the unsubscribe has nothing left to accomplish — or capture the original and rethrow it.

Found by a review sweep over main while resolving #192; not introduced by it.

Start in packages/nats/src/JetStream/Consumer.php at Consumer::fetch() and trace Subscription::unsubscribe() through Connection::unsubscribe() to Connection::send(). Reproduce or cover a fetch failure during teardown, then verify the original exception remains visible while cleanup still occurs without replacing it with a reconnect failure.