docs: reorder & testing

integration/testenv/images.go

@@ -61,6 +61,13 @@ func EnsureGameImage(t *testing.T) {
 	}
 }
 
+// integrationImageLabel is the docker label stamped onto every image
+// built from `integration/testenv/images.go`. The pre-clean script
+// (`integration/scripts/preclean.sh`) keys off this label to wipe
+// stale builds without touching testcontainers-pulled service images
+// (postgres, redis, ryuk, mailpit) which we want to keep cached.
+const integrationImageLabel = "galaxy.test.kind=integration-image"
+
 func buildImage(tag, dockerfile string) error {
 	root, err := workspaceRoot()
 	if err != nil {
@@ -72,6 +79,7 @@ func buildImage(tag, dockerfile string) error {
 	cmd := exec.CommandContext(ctx, "docker", "build",
 		"-t", tag,
 		"-f", filepath.Join(root, dockerfile),
+		"--label", integrationImageLabel,
 		root,
 	)
 	out, err := cmd.CombinedOutput()