🛟 fix: Auto-Recover from Stale Service Worker Assets After Deploys (#13686)

* 🛟 fix: Auto-Recover from Stale Service Worker Assets After Deploys

- 404 missing static assets in the SPA fallback instead of serving index.html
- inline recovery script unregisters stale SWs and reloads once on chunk failure
- route vite:preloadError into the same recovery path for stale lazy chunks

* 🛟 fix: Address Review — SW-Side Recovery, Scoped Unregister, Shared Fallback

- importScripts'd sw-heal.js pings window clients on activation and reloads
  ones that can't pong: stale pages carry no recovery code of their own
- scope SW unregistration to the deployment base for subpath installs
- preventDefault vite:preloadError only when a recovery reload was initiated
- extract createSpaFallback and apply the asset 404 guard to experimental.js

api/server/utils/fallback.js

@@ -0,0 +1,20 @@
+/** Static asset extensions that must 404 when missing — serving the SPA's
+ * index.html for them breaks strict MIME checks and poisons SW/browser caches. */
+const STATIC_ASSET_EXT =
+  /\.(?:js|mjs|css|map|json|wasm|webmanifest|png|jpe?g|gif|svg|ico|webp|avif|woff2?|ttf|otf|eot)$/i;
+
+/**
+ * Creates the SPA fallback middleware: serves index.html for unmatched
+ * routes while returning 404 for missing static assets.
+ * @param {(req: import('express').Request, res: import('express').Response) => void} sendIndexHtml
+ */
+function createSpaFallback(sendIndexHtml) {
+  return (req, res) => {
+    if (STATIC_ASSET_EXT.test(req.path)) {
+      return res.status(404).end();
+    }
+    return sendIndexHtml(req, res);
+  };
+}
+
+module.exports = createSpaFallback;

api/server/utils/staticCache.js

@@ -38,7 +38,8 @@ function staticCache(staticPath, options = {}) {
       fileName === 'index.html' ||
       fileName.endsWith('.webmanifest') ||
       fileName === 'manifest.json' ||
-      fileName === 'sw.js'
+      fileName === 'sw.js' ||
+      fileName === 'sw-heal.js'
     ) {
       res.setHeader('Cache-Control', 'no-store, no-cache, must-revalidate');
     } else {