Resuming a session has strange ux with regards to model and reasoning

### Describe the bug

If you have a session that's was done on `gpt-5.6-terra` with `medium`, and you `--resume` it, with either `--model=gpt-5.6-luna --reasoning-effort=xhigh` or `gpt-5.6-luna + xhigh` in your `~/.copilot/settings.json`, the `reasoningEffort` is honoured, but the model is not, and your resumed session will be on `gpt-5.6-terra xhigh`

Feels like this should be consistent? It should either:

- Explicitly honour the original session, keeping the settings the same
- Explicitly honour your copilot CLI args and/or settings.json

I would rather the latter personally, but raising this as a UX bug.

This also affects sessions resumed via copilot-sdk.

### Affected version

1.0.77

### Steps to reproduce the behavior

_No response_

### Expected behavior

_No response_

### Additional context

_No response_

从 --resume 流程开始，跟踪恢复会话时如何应用 --model、--reasoning-effort 和 ~/.copilot/settings.json。也检查相应的 copilot-sdk resume 路径。当为 CLI 会话和 SDK 会话选择的优先级保持一致，并且 model 和 reasoning effort 具有回归覆盖时，即表示完成。

由索引模型根据 Issue 内容生成。