Add release smoke path for pre-store verification (WP-0002)

Introduce npm run smoke with automated build, test, lint, dist, and
metadata-only compliance checks. Document manual Chrome steps in
RELEASE_SMOKE.md and fix unused imports blocking lint.

package.json

@@ -12,7 +12,8 @@
     "test:watch": "jest --watch",
     "lint": "eslint src/**/*.{js,ts}",
     "lint:fix": "eslint src/**/*.{js,ts} --fix",
-    "type-check": "tsc --noEmit"
+    "type-check": "tsc --noEmit",
+    "smoke": "bash scripts/release-smoke.sh"
   },
   "keywords": [
     "chrome-extension",