Keyboard navigation does not scroll the `/` command popup

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### Search first

- [x] I searched and no similar issues were found

### What Happened?

When using the `/` command popup, navigating through the items with the **Up/Down arrow keys** does not scroll the popup.

As a result, keyboard navigation does not work properly when navigating through items beyond the currently visible area.

### Reproduce the Bug

1. Create or edit a block.
2. Type `/` to open the command popup.
3. Use the **Up/Down arrow keys** to navigate through the commands.
4. Continue navigating until the selected item moves beyond the currently visible area.

### Expected Behavior

The popup should automatically scroll to keep the currently focused item visible when navigating with the Up/Down arrow keys.

### Screenshots

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### Files

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### Browser, Desktop or Mobile Platform Information

windows 11
logseq 2.0.1-alpha+nightly.20260907

### Additional Context

_No response_

### Are you willing to submit a PR? If you know how to fix the bug.

- [ ] I'm willing to submit a PR (Thank you!)

Reproduce the issue in a block editor by opening the `/` command popup and navigating with the Up/Down arrow keys. Trace the popup's keyboard-navigation entry point and verify that the focused command remains visible while moving beyond the current viewport.

Written by the indexing model from the issue text.