CmdPal: fallback order unsynced access to command list during reload

### Microsoft PowerToys version

0.97

### Installation method

PowerToys auto-update

### Area(s) with issue?

Command Palette

### Steps to reproduce

Command Palette fallback order operates on the top-level command list while it is still loading. As a result, the list may be incomplete, which can cause the saved state to be trimmed against a partially loaded command set.

How to break it?

1. Install a large number of extensions.

1. Quit Command Palette.

1. Launch Command Palette again.

1. While extensions are still loading, change the fallback order.

### ✔️ Expected Behavior

_No response_

### ❌ Actual Behavior

_No response_

### Additional Information

_No response_

### Other Software

_No response_

Start with Command Palette's fallback-order handling and the extension-loading path described in the reproduction steps. Reproduce with many extensions, relaunch Command Palette, and change the fallback order while loading. Done means fallback order does not use an incomplete command list and saved state is not trimmed against partially loaded commands.

Written by the indexing model from the issue text.