refactor(ui): drop the unused panel drag and position code

No markup carries a drag handle, so nothing called it: panel position
controls keep only collapsed state and the layout-reset notice.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

scripts/qa-ui-disposal.mjs

@@ -139,7 +139,6 @@ try {
       const focusBefore = document.activeElement;
       const stoppedBeforeRestoration =
         ui._panelLayout.destroyed &&
-        ui._panelPosition.destroyed &&
         ui._feedback.destroyed &&
         ui._recording.destroyed &&
         cockpit.destroyed &&