Local changes made after resuming a cloud agent session cannot be resumed

### Describe the bug

When a Copilot cloud agent session is resumed locally and then continued from the CLI, the new local messages and changes do not seem to be saved as a resumable local session.

After closing the local session, there does not appear to be any way to resume the locally modified version of the session.

Running `copilot --resume` does not list the local session.

Running `copilot --resume=` with the UUID returned by the closed local session tries to resume the original remote/cloud session instead, without any of the messages or changes that were added locally.

This makes the local continuation workflow unreliable because once the locally resumed session is closed, the local context is lost and only the original remote session can be resumed.

### Affected version

1.0.59

### Steps to reproduce the behavior

1. Use GitHub cloud agents to create a new session in a repository.
2. In a local checkout of the same repository, run:
```bash
copilot --resume=
```
using the UUID from the cloud agent session.
3. Continue the session locally by sending new messages and making progress in the CLI.
4. Close the local Copilot CLI session.
5. Try to resume the session again.

### Expected behavior

After continuing the cloud agent session locally, the locally updated session should be resumable.

For example:

```bash
copilot --resume
```

should list the locally continued session, or:

```bash
copilot --resume=
```

should resume the locally updated version of the session, including the messages and context added after it was brought local.

### Additional context

OS: Ubuntu 24.04

Start with the CLI resume entry points exercised by `copilot --resume` and `copilot --resume=`, reproducing the flow from a cloud session to local continuation and closure. Trace how the local messages and changes are persisted and selected for resumption; done means the continued session appears in `--resume` and the UUID resumes the locally updated context.

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