## Why
Clients using `thread/read` with `includeTurns: true` need the legacy full-history
view even when a thread stores its history in paginated form.
## What changed
- Reconstruct full projected turns from paginated history for both stored and
loaded threads.
- Keep `thread/turns/list` and `thread/items/list` as the preferred incremental
history APIs.
## Testing
- Cover `thread/read(includeTurns=true)` before and after a paginated thread is
loaded.
GitOrigin-RevId: 6efdc04e5ed3cad2ff2078d8103933082c7921db