[Remote rendering 3.6] Save/load end-to-end verification and remove remaining reapply scaffolding

### 📝 Description of the feature

Confirm that the full RuntimeAppState round trip is correct and complete now that every state class is server-authoritative, and for any client-side state reapplication scaffolding that remains, remove it.

The intent was for each of the individual user stories in Phase 3 to have synced back the property state to the server, so that the client-side reapplication of the cached client-side state was no longer needed and removed for that property.

In this story, we:

- verify the end to end save/load state works as expected, and
- verify that no unnecessary client-side reapplication of state remains.

### Acceptance Criteria

save/load state works as expected

### 💵 Business Value

_No response_

### 🔗 Useful links and references

_No response_

Start by tracing the RuntimeAppState save/load path and reviewing the Phase 3 state classes for remaining client-side reapplication scaffolding. Verify the complete state round trip end to end, then confirm that unnecessary client-side reapplication is removed and save/load behaves as expected.

索引モデルが issue の本文から書いたものです。