convert on input entry (remove need for Play/Convert button)

**Is your feature request related to a problem? Please describe.**
Pushing the Play/"Convert" button is an extra step.

**Describe the solution you'd like**
Conversions to happen whenever input is added or modified. No buttons needed.

Start by running the website and locating the input handling and Play/Convert button entry points. Trace where conversions are triggered when input is added or modified, then verify that conversion happens without the button and that the existing serialization and deserialization behavior remains available.

Written by the indexing model from the issue text.