Worktree configuration not respected

### Short summary

Even though `Worktree location` is configured as `Next to repository`, a worktree was created under `.copilot` in my home directory

### Affected version or release

v1.1.4

### Installation context

Installed on Windows 11, working against a public GitHub project checked out in my WSL Ubuntu environment

### What happened?

Worktree was not created at the expected location; it seemed to ignore the configuration entirely.

### Steps to reproduce

First I changed my GitHub Copilot App configuration to check out worktrees _beside_ the main repo:

Then I added an existing repo checkout from my WSL Ubuntu environment

```
/home/bevan/github/azure-service-operator
```

Finally, I started a new session within that project, asking Copilot to make a simple change (mostly as a test).

The session promptly created a worktree in the wrong place:

The full path used is:
```
/home/bevan/.copilotd/worktrees/wsl:Ubuntu/azure-service-operator/theunrepentantgeek-fluffy-dollop
```

### Expected behavior

I expected the worktree to be located at

/home/bevan/github/azure-service-operator-worktrees/theunrepentantgeek-fluffy-dollop

(Side note: A useful branch name would be much preferred to this kind of noise. It's better than a GUID but only barely.)

### Additional context

_No response_