improve stats action performance metrics

- Lower regression thresholds to 10ms/2% and 1KB/1% to catch all meaningful Next.js regressions
- Add 3-decimal precision for seconds (1.234s instead of 1.2s)
- Rename metrics: 'Boot/Ready' -> 'Listen/First Request' for clarity
- Emphasize Turbopack (default), collapse Webpack as legacy
- Add single glossary instead of 5 repetitive dropdowns
- Simplify group names (no 'Turbopack' prefix since it's default)

Author: feedthejim

.github/actions/next-stats-action/action.yml

@@ -0,0 +1,10 @@
+name: 'Next.js PR Stats'
+description: 'Compare PR stats with canary'
+inputs:
+  bundler:
+    description: 'Bundler to benchmark (webpack|turbopack|both)'
+    default: 'both'
+    required: false
+runs:
+  using: 'docker'
+  image: 'Dockerfile'

.github/actions/next-stats-action/package.json

@@ -2,6 +2,7 @@
   "private": true,
   "main": "src/index.js",
   "dependencies": {
+    "@vercel/kv": "^1.0.1",
     "async-sema": "^3.1.0",
     "execa": "2.0.3",
     "get-port": "^5.0.0",