Overlay renderer system

Status: implemented. The former proposal in this file has been superseded by the overlay SDK and theme registry in src/overlay/README.md.

Production flow#

Worker public projection + live-run projection
                    ↓
        src/overlay/sources/live.ts
                    ↓
 OverlayProvider → normalized snapshot → OverlayRenderer
                    ↓
     registered channel theme at /overlay?channel=ID

• /overlay?channel=ID is the transparent public OBS browser source.
• /overlay/studio?channel=ID is the authenticated design/test surface. Its Game and Events tabs use the mock source and never mutate a real session.
• Theme selection, primitive per-theme settings, and element visibility are stored per Channel in D1 and included in the public projection.
• The Worker validates IDs, value types, entry counts, and payload size. React theme schemas resolve the specific defaults used by a renderer.
• Unknown theme IDs fall back to the first registered theme, Broadcast.
• Public clients never receive owner secrets, session cookies, invite tokens, integration tokens, or administrative challenge state.

Adding a theme#

1. Add the theme folder under src/overlay/themes/ using the SDK contracts.
2. Register it in src/overlay/themes/index.ts.
3. Keep its ID stable and its settings declarative; do not evaluate runtime JavaScript, HTML, or CSS from stored configuration.
4. Exercise its scenes and controls in /overlay/studio, then run npm test and npm run build.

Setup, Settings → Theme, the studio, and the live overlay all discover the same registry, so no route-specific theme list should be added.