Right sidebar cannot load an attached empty non-Git folder

### Before filing

- [x] I searched open and closed issues for duplicates.
- [x] I reproduced this on the latest release (Berd 0.6.2).
- [x] This is one bug, not several bundled together.

### Closest existing issue

None found.

### What's broken

The right-side workspace browser fails to load an attached empty, non-Git directory, even though Berd records the folder correctly and the agent can access it. The displayed recovery action, “Try again,” does not respond.

### Steps to reproduce

1. Launch Berd 0.6.2 on macOS.
2. Open a Goose chat whose working directory is an empty, non-Git directory. The issue was reproduced with both an existing chat and another session attached to the same directory.
3. Open the right sidebar and view the Context, Changes, or Files area.
4. Observe “Couldn't load this folder. Try again.”
5. Click “Try again.”
6. Observe that nothing happens and the folder remains unloaded.

The affected folder existed, was readable by the current user, and had standard `drwxr-xr-x` permissions. The model is not relevant to this app-shell file-browser behavior. Whether the affected chats had prior transcript history was not recorded.

### What you expected to happen

The right sidebar should display an attached directory even when it is empty and not a Git repository. If loading fails, “Try again” should retry the operation.

### What actually happened

The folder remained on the “Couldn't load this folder” state. “Try again” did not respond. Collapsing and reopening the sidebar, switching chats, and restarting Berd did not resolve it.

### How often does it happen?

Every time in two sessions attached to the affected directory.

### Berd version

0.6.2 (the latest release at the time of filing)

### Operating system

macOS (Apple Silicon)

### Model and provider

n/a — this concerns the app-shell workspace browser. The affected sessions used the Goose harness; the originally recorded model was `gpt-5.6-sol`, provider unknown.

### Relevant log output

```text
No relevant log output. The app log was checked for folder-loading or sidebar errors around the reproduction period.
```

### Screenshots, recordings, or other context

No screenshot or recording is attached yet. The visible error text was: “Couldn't load this folder. Try again.”

No source file or test is named; start at the desktop app's right-sidebar workspace browser and reproduce the failure with an empty, non-Git directory on macOS. Trace the folder-loading and “Try again” entry points, then verify that the directory renders and that retry performs a new load when loading fails.

Written by the indexing model from the issue text.