fix: remove dead model config code for true zero-config

- Remove unused model.type validation that caused Workshop error
- Remove model config from BrainyConfig type (never used)
- Simplify modelAutoConfig.ts (always Q8 WASM)
- Clean up zeroConfig.ts model references

This fixes the "Invalid model type: balanced" error and removes
unnecessary configuration options that did nothing.

src/config/index.ts

@@ -3,19 +3,13 @@
  * Main entry point for all auto-configuration features
  */
 
-// Model configuration
-export { 
-  autoSelectModelPrecision, 
-  ModelPrecision as ModelPrecisionType,  // Avoid conflict
-  ModelPreset,
+// Model configuration (simplified - always Q8 WASM)
+export {
+  getModelPrecision,
   shouldAutoDownloadModels,
-  getModelPath,
-  logModelConfig
+  getModelPath
 } from './modelAutoConfig.js'
 
-// Model precision - Always Q8 now (99% accuracy, 75% smaller)
-export const getModelPrecision = () => 'q8' as const
-
 // Storage configuration
 export { 
   autoDetectStorage,