Add Ghostty terminal, session recovery, voice asset caching, and gitignore large assets

Integrates ghostty-web and node-pty packages, adds tmux session recovery on startup,
refactors WebSocket transport to noServer mode, caches Sherpa voice model assets via
service worker. Large assets (sherpa, ghostty-vt.wasm, fonts) are now gitignored as
they are copied from the webterm project.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitignore

@@ -11,3 +11,8 @@ docs/
 .server.pid
 
 .bkit/
+
+# Large assets copied from webterm project — not tracked in git
+public/sherpa-moonshine-v2-base-en/
+public/ghostty-vt.wasm
+public/fonts/