## Why
A yielded code mode cell can emit a notification after the session switches models. Its output should retain the originating model's truncation budget instead of using the receiving model's budget.
## What changed
Carry the cell's output token limit, including the serialization allowance, through notification dispatch and attach it as `history_truncation_token_limit` metadata. Allow `inject_if_running` to accept response item envelopes so queued notifications preserve this metadata in history and rollouts.
## Testing
Add regression coverage for delayed notifications across a model switch, verifying per-cell truncation budgets, full notification text in raw events, and persisted rollout metadata. Add a task-completion test that checks notification budgets are preserved alongside queued user input.
GitOrigin-RevId: 28380a039a6d41ea324401fcf1f611d81a279477
122d55cba8