feat: add intelligent storage auto-detection as default

- Change default storage from 'memory' to 'auto' for smart environment detection
- Add 'auto' support to storage type validation and TypeScript types
- Browser: auto-selects OPFS → memory fallback
- Node.js: auto-selects filesystem → memory fallback
- Cloud: auto-detects S3/GCS/R2 → disk → memory fallback
- Eliminates need for manual storage configuration in most cases

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/types/brainy.types.ts

@@ -311,7 +311,7 @@ export type AggregateMetric =
 export interface BrainyConfig {
   // Storage configuration
   storage?: {
-    type: 'memory' | 'filesystem' | 's3' | 'r2' | 'opfs'
+    type: 'auto' | 'memory' | 'filesystem' | 's3' | 'r2' | 'opfs' | 'gcs'
     options?: any
   }