CmdPal: Fix dock subtitle visibility in compact mode after async update (#48088)

## Summary

When an extension updates its `Subtitle` property asynchronously after
initial render, the `TextVisibilityStates` visual state group
transitions from `TitleOnly` → `TextVisible`. This transition sets
`SubtitleText.Visibility = Visible`, overriding the `CompactStates`
setter that had hidden it.

## Fix

Added `control.UpdateCompactState()` to `OnTextPropertyChanged` in
`DockItemControl.xaml.cs`. This re-applies the compact state after any
text property change. When `IsCompact` is `false`, `UpdateCompactState`
is a no-op — no behavior change for the non-compact path.

Fixes #47980

Co-authored-by: root <root@io.bbq>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>