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>

cmd/gbrgames/import_test.go

@@ -0,0 +1,48 @@
+package main
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"reflect"
+	"testing"
+)
+
+// Whatever the panel exports must come back unchanged after import and export.
+func TestImportRoundTrip(t *testing.T) {
+	game := map[string]any{
+		"id": "round-trip", "name": "Round Trip", "defaultDockerImage": "debian:12", "installMethod": "NONE",
+		"defaultStartupCommand": "./start.sh -log",
+		"requiredMemoryMb":      float64(4096),
+		"configFormatOptions": map[string]any{
+			"separator": "\n", "footer": "\n", "header": "[Section]\n", "assignment": "=", "space": " ",
+			"multi": "[A]\nOptionSettings=(", "quoteStrings": true,
+		},
+		"installConfig": map[string]any{"script": "#!/bin/bash\nset -e\necho hi\n"},
+		"defaultConfig": map[string]any{"Rate": "1.000000", "Port": float64(7777), "Empty": "", "Ratio": 0.5},
+	}
+
+	dir := t.TempDir()
+	path := filepath.Join(dir, "game.yaml")
+	if err := writeGame(path, game); err != nil {
+		t.Fatal(err)
+	}
+	raw, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	loaded, err := loadYAML(raw)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	// Compare as JSON, the way the panel receives it
+	var got, want any
+	gotJSON, _ := json.Marshal(loaded)
+	wantJSON, _ := json.Marshal(game)
+	json.Unmarshal(gotJSON, &got)
+	json.Unmarshal(wantJSON, &want)
+	if !reflect.DeepEqual(got, want) {
+		t.Fatalf("round trip changed the template\n got: %s\nwant: %s\nyaml:\n%s", gotJSON, wantJSON, raw)
+	}
+}