Copilot dumps output into prose instead of tool call etc.

### Short summary

App fails to make tool calls, and instead dumps output into the chat window

### Affected version or release

v0.2.34

### Installation context

app installed on my windows surface laptop

### What happened?

Instead of making the actual code change, it just dumped the content into chat output:

I was using interactive mode, claude opus 4.8 1M moduel, high reasoning, in a worktree session. using latest build at time of this issue open.

### Steps to reproduce

_No response_

### Expected behavior

_No response_

### Additional context

_No response_

No files, tests, or entry points are mentioned. Start by reproducing the failure in interactive mode with the stated Windows, worktree, model, and reasoning settings; compare the chat output with the expected tool-call behavior. Done means the application makes the tool call and applies the requested code change.

索引モデルが issue の本文から書いたものです。