[Bug]: Default Merge Action not respected

### Platform

macOS

### Operating system version

macOS Tahoe 26.3.1 (a)

### System architecture

ARM64 (M1, M2, etc)

### PolyScope Version

0.17.0

### Bug description

The default merge action is no longer respected. It always goes to merge locally, even though I have the default merge action set to create a pull request.

### Steps to reproduce

In Settings, under Behavior, set the default merge action to "Create Pull Request." Then, in a workspace, observe that the button says "Merge" and not "Create Pull Request".

### Relevant log output

```shell

```

Start in Settings under Behavior and trace how the default merge action is read when a workspace shows its merge button. Reproduce with the default set to "Create Pull Request"; done means the button displays "Create Pull Request" instead of "Merge" and the setting remains respected.

Written by the indexing model from the issue text.