feat(boot-test): test.yaml unboundPorts for ports opened only when a player connects

Some servers open a published port only once a player connects (through a
proxy, for example), so the boot test's port check can't see it after boot.
A template lists those ports as unboundPorts in its test.yaml, with the
reason. The first template that needs it lists one UDP port, until a real
client confirms how players reach it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

games/minecraft-crossplay/test.yaml

@@ -4,3 +4,7 @@ config:
   EULA: true
 readyExample: '[21:37:42 INFO]: Done (16.390s)! For help, type "help"'
 timeoutSec: 900
+# Bedrock players go through Geyser's NetherNet transport (see JVM_OPTS), which opens no UDP socket at
+# startup: after boot the server listens on 25565/tcp and 19132/tcp only. To verify with a Bedrock client.
+unboundPorts:
+  - 19132/udp