feat(reliability): implement automatic offline model detection for production

Add @soulcraft/brainy-models as optional dependency for zero-config offline reliability. Enhance robustModelLoader with hierarchical loading strategy (local → online → fail). Add comprehensive production deployment documentation and update README with clear benefits.

This solves critical production issues where Universal Sentence Encoder fails to load in Docker/Cloud Run environments due to network timeouts or blocked URLs. The solution provides 100% offline reliability while maintaining backward compatibility and requires no code changes from users.

rollup.config.js

@@ -284,7 +284,9 @@ const mainConfig = {
     'node:fs',
     'node:path',
     'fs',
-    'path'
+    'path',
+    // Optional dependency - externalize to allow graceful failure
+    '@soulcraft/brainy-models'
   ]
 }
 
@@ -330,7 +332,9 @@ const workerConfig = {
     'node:fs',
     'node:path',
     'fs',
-    'path'
+    'path',
+    // Optional dependency - externalize to allow graceful failure
+    '@soulcraft/brainy-models'
   ]
 }