CCR is not triggered when assigned to Copilot from PR

### Short summary

CCR is not triggered when assigned to Copilot from PR

### Affected version or release

v1.0.19

### Installation context

Just normal install

### What happened?

1. Create a session and do something to make code changes in a worktree
2. Open a PR
3. Assign Copilot as a "Reviewer"
4. CCR should be triggered, but it is not, i have to go to the website to request

ALSO, if you assign copilot as an assignee it will trigger a new cloud agent session, which is weird

### Steps to reproduce

_No response_

### Expected behavior

_No response_

### Additional context

_No response_

Reproduce the workflow from the issue: create a session with worktree changes, open a PR, and assign Copilot as a reviewer rather than an assignee. Compare that behavior with assigning Copilot directly and requesting from the website; done means reviewer assignment triggers CCR without starting an unexpected cloud agent session.

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