feat(tts): integrate autonomous Piper neural TTS with zero-latency pre-warming for words and context

app/static/sw.js

@@ -1,7 +1,7 @@
 // Service Worker for Notes English PWA (Stage 2)
 // Strategy: Cache-first for static assets, Network-first for API calls.
 
-const CACHE_NAME = 'notes-v6.3';
+const CACHE_NAME = 'notes-v6.4';
 const OFFLINE_URL = '/';
 
 const PRECACHE_URLS = [