fix: validate --listen port numbers instead of crashing with RangeError

[charan-rathore]

Related Issues

No tracking issue; found while testing the CLI.

Description

Changed

• parseEndpoint now checks that a numeric endpoint is an integer from 0 to 65535 and throws Invalid port number: <value> otherwise, for both bare ports and tcp:// endpoints. Before, serve --listen 99999 (also negative, fractional, non-finite, or tcp://host:99999) went straight to the socket layer and crashed with a raw RangeError [ERR_SOCKET_BAD_PORT] stack trace.
• The error is thrown the same way as the existing invalid-endpoint errors.
• Added 5 cases to the existing invalidEndpoints table in tests/cli.test.ts, and a patch changeset.

Caveats/Problems/Issues

Exactly the 5 new cases fail on the unpatched base; tests/cli.test.ts passes 16/16 with the change. Compiled CLI: --listen 99999 and --listen 3000.5 print "Invalid port number: ..." and --listen 4117 serves HTTP 200. Tests ran through pnpm test (the repo config); bare vitest shows a help-text snapshot mismatch that is also present on the base.

Checklist

• The issues that this PR fixes/closes have been mentioned above.
• What this PR adds/changes/removes has been explained.
• All tests (pnpm test) pass.
• The linter (pnpm lint) does not throw an errors.
• All added/modified code has been commented, and
  methods/classes/constants/types have been annotated with TSDoc comments.

[vercel]

@charan-rathore is attempting to deploy a commit to the Internal Playground Team on Vercel.

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[charan-rathore]

This one has been quiet, so I am closing it for now. Happy to reopen if it becomes useful.