fix: fail closed on unusable Codex auth during sandbox auth merge

When reusing a Codex sandbox, the workspace-restore step now performs
an auth-merge check before adopting the sandbox's auth.json. The merge
fails closed when:

- host or sandbox Codex auth is unusable (missing token or account)
- the subscription payload shapes differ between host and sandbox
- subscription account identities do not match

Additional hardening: node absence on PATH during the embedded decision
script now exits non-zero instead of silently falling through. Co-change
comments link parseAuth (the embedded script) to hasUsableAuthPayload
(codex-home.ts) so a future auth-format change cannot silently diverge
between the two implementations.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

packages/plugins/examples/plugin-authoring-smoke-example/package.json

@@ -0,0 +1,45 @@
+{
+  "name": "@paperclipai/plugin-authoring-smoke-example",
+  "version": "0.1.0",
+  "type": "module",
+  "private": true,
+  "description": "A Paperclip plugin",
+  "scripts": {
+    "prebuild": "pnpm --filter @paperclipai/plugin-sdk ensure-build-deps",
+    "build": "node ./esbuild.config.mjs",
+    "build:rollup": "rollup -c",
+    "dev": "node ./esbuild.config.mjs --watch",
+    "dev:ui": "paperclip-plugin-dev-server --root . --ui-dir dist/ui --port 4177",
+    "test": "vitest run --config ./vitest.config.ts",
+    "typecheck": "pnpm --filter @paperclipai/plugin-sdk ensure-build-deps && tsc --noEmit"
+  },
+  "paperclipPlugin": {
+    "manifest": "./dist/manifest.js",
+    "worker": "./dist/worker.js",
+    "ui": "./dist/ui/"
+  },
+  "keywords": [
+    "paperclip",
+    "plugin",
+    "connector"
+  ],
+  "author": "Plugin Author",
+  "license": "MIT",
+  "dependencies": {
+    "@paperclipai/plugin-sdk": "workspace:*"
+  },
+  "devDependencies": {
+    "@rollup/plugin-node-resolve": "^16.0.1",
+    "@rollup/plugin-typescript": "^12.1.2",
+    "@types/node": "^22.19.21",
+    "@types/react": "^19.2.17",
+    "esbuild": "^0.28.1",
+    "rollup": "^4.62.2",
+    "tslib": "^2.8.1",
+    "typescript": "^5.7.3",
+    "vitest": "^4.1.8"
+  },
+  "peerDependencies": {
+    "react": ">=18"
+  }
+}