A lighter caption engine.

Use a smaller CPU-only runtime to address caption startup failures on Safari.

In this release

Improved
Captions now use the standard CPU-only speech runtime, avoiding a runtime variant associated with Safari memory spikes. The runtime binary is roughly half the size.
Improved
Matching caption runtime assets are served with the app and cached for reuse instead of relying on a separate runtime CDN.
Validation
Real speech transcription passes desktop browser checks on first start, reuse, and worker restart. Confirmation on affected iPhones is still needed.