## Why
App widgets need to read resources using the app and account context of the
tool call that produced them, including after a thread is restored.
## What changed
- Add an optional `originCallId` to `mcpServer/resource/read` requests and
return it on successful scoped reads.
- Track bounded provenance for successful app tool calls in thread history and
use the current tool binding, account link, and app policy when reading the
associated widget resource.
- Reject missing, mismatched, failed, or ambiguous origins, while keeping
app-only tools available for widget reads without exposing them to the model.
## Testing
Add app-server coverage for scoped widget reads across both history modes,
ephemeral and persistent threads, server restarts, app-only visibility, and
invalid origin cases.
GitOrigin-RevId: 11eaefc066b2a3b639599e4cbdef680233d150a2
880f1135ea