ci: boot-test changed games before publishing

Only games whose folder changed are boot-tested (against the previous
main commit, or against main on branches; manual runs pick games). Each
one is deployed by the node-agent's real deploy code on a dedicated
game-test runner, in a network that can reach the internet but not the
LAN. Publishing to the panel runs only if they all booted.

- boottest-payload builds the DEPLOY_SERVER message the panel would send
- readyPattern/failPatterns in game.yaml; readyExample in test.yaml is
  checked against the pattern during validation
- secrets in test.yaml come from CI; a game missing one is skipped
- Minecraft gets a ready pattern; Dragonwilds needs DRAGONWILDS_OWNER_ID
- RUNNER.md + scripts/runner: runner, isolated network, systemd unit

Also fixes newline values ("\n" separators/footers) that yaml.v3 wrote
as "" on import, which would have broken ARK and Dragonwilds config
files once synced, and adds a round-trip test for the importer.

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

scripts/runner/docker-compose.yml

@@ -0,0 +1,17 @@
+# The game-test runner: a second act_runner next to the build runner, so long boot tests
+# (ARK installs take 20+ minutes) never hold up builds. One job at a time.
+services:
+  game-test-runner:
+    image: gitea/act_runner:0.6.1
+    container_name: gitea-game-test-runner
+    restart: unless-stopped
+    environment:
+      GITEA_INSTANCE_URL: https://www.gitea.gbreed.com
+      GITEA_RUNNER_REGISTRATION_TOKEN: ${GITEA_RUNNER_REGISTRATION_TOKEN}
+      GITEA_RUNNER_NAME: game-test
+      GITEA_RUNNER_LABELS: game-test:docker://catthehacker/ubuntu:act-latest
+      CONFIG_FILE: /config.yaml
+    volumes:
+      - ./config.yaml:/config.yaml:ro
+      - ./data:/data
+      - /var/run/docker.sock:/var/run/docker.sock