fix: Gemma4 worker must be classic type — module worker breaks CDN dynamic import

Root cause: initAiWorker creates workers with {type:'module'} but ai-worker-gemma4.js
uses dynamic import() of external CDN URL (jsdelivr transformers.js). In Vite dev
mode, module workers have their imports intercepted by the bundler which cannot
resolve https://cdn.jsdelivr.net/... URLs, causing immediate worker.onerror and
the 'Worker failed to initialize' message in the consent modal.

Fix:
- ai-assistant.js: read cfg.workerType; default 'module' for existing workers
- ai-models.js: workerType:'classic' on gemma4-e2b and gemma4-e4b
- ai-worker-gemma4.js: unhandledrejection safety net, try/catch in message
  handler, null-check for Gemma4ForConditionalGeneration/Gemma4Processor

Author: ijbo

changelogs/CHANGELOG-gemma4-worker-classic-fix.md

@@ -0,0 +1,5 @@
+# Fix: Gemma 4 Worker Init — classic worker type + error handling
+
+- ai-assistant.js: read `workerType` from model config (default: module); Gemma 4 workers must be classic, not module workers, because Vite dev mode intercepts module worker imports and fails to resolve external CDN URLs via its module bundler
+- ai-models.js: added `workerType: "classic"` to gemma4-e2b and gemma4-e4b configs
+- ai-worker-gemma4.js: added unhandledrejection handler, try/catch in message handler, null-checks for Gemma4 classes with readable error messages

js/ai-assistant.js

@@ -697,7 +697,11 @@
     const workerPath = (cfg && cfg.workerFile) || 'ai-worker.js';
     // Add cache-buster for local workers in dev mode so edits are always picked up
     const workerUrl = workerPath + '?v=' + (window._workerVersion || Date.now());
-    const worker = new Worker(workerUrl, { type: 'module' });
+    // Some workers (e.g. gemma4) use dynamic import() of external CDN URLs.
+    // These MUST be classic workers — module workers in Vite dev mode have their
+    // imports intercepted by the module bundler, causing CDN imports to fail.
+    const workerType = (cfg && cfg.workerType) || 'module';
+    const worker = new Worker(workerUrl, { type: workerType });
     ls.worker = worker;
 
     // Send model ID before loading

js/ai-models.js

@@ -103,6 +103,7 @@
             category: 'local-multimodal',
             localModelId: 'onnx-community/gemma-4-E2B-it-ONNX',
             workerFile: 'ai-worker-gemma4.js',
+            workerType: 'classic', // Must be classic — uses dynamic import() of CDN URL
             downloadSize: '~2 GB',
             requiresWebGPU: true,
             supportsVision: true,
@@ -124,6 +125,7 @@
             category: 'local-multimodal',
             localModelId: 'onnx-community/gemma-4-E4B-it-ONNX',
             workerFile: 'ai-worker-gemma4.js',
+            workerType: 'classic', // Must be classic — uses dynamic import() of CDN URL
             downloadSize: '~4 GB',
             requiresWebGPU: true,
             requiresHighEnd: true,