test(snapshot): drive ordinary turns through headless dsh

vitest.snapshot.config.ts

@@ -51,6 +51,7 @@ export default defineConfig({
       ...(process.env.DSH_EXAMPLE_MODE === 'lib' ? ['apps/web/tests/**/*.snapshot.ts'] : []),
       'apps/cli/tests/**/*.snapshot.ts',
       'examples/*/tests/**/*.snapshot.ts',
+      'snapshots/**/*.snapshot.ts',
     ],
     // Replay never writes committed outputs and every scenario owns its
     // mutable runtime state (the subprocess suites use a unique temp dir and