Keep immersive owner and mode atomic

[hamzamerzic]

Summary

• keep the immersive holder and presentation mode in one reducer-owned request
• replay each frame’s exact mode during live promotion
• replace contradictory canvas booleans with one applied mode
• keep hold bindings in runtime-owned weak state and remove the unused timing option

Why

The bar-collapse change stored ownership and mode separately, so a frame promotion or later holder could inherit stale presentation state. This follow-up makes invalid combinations unrepresentable and narrows the runtime and host seams without changing the interaction.

Follow-up to #722.

Testing

• npm test
• npm run lint -- --quiet
• npm run build
• npm run runtime:check