Three issues caused the port to remain bound after partial failures:
1. VoiceCallWebhookServer.start() had no idempotency guard — calling it
while the server was already listening would create a second server on
the same port.
2. createVoiceCallRuntime() did not clean up the webhook server if a step
after webhookServer.start() failed (e.g. manager.initialize). The
server kept the port bound while the runtime promise rejected.
3. ensureRuntime() cached the rejected promise forever, so subsequent
calls would re-throw the same error without ever retrying. Combined
with (2), the port stayed orphaned until gateway restart.
Fixes#32387
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
e707c97ca6