Compare Settings Bar

Displays Compare Mode specific options on screen while Compare Mode is not "Off".

For MVP, this should include:

1. Current Layer (A, B, C, etc). These should be clickable?
2. Compare Offset (no of frames to offset)
3. Sync Point (first frame, same frame number, etc)
4. Compare Scope ("All Media" or "Selected Media"). If "All Media" is selected then everything in the PSC should be displayed whether it is selected or not. Otherwise only the "Selected Media" should be visible.

Start by locating the Compare Mode settings bar and the existing Compare Mode state handling. Implement the MVP controls for current layer, compare offset, sync point, and compare scope, including the stated visibility behavior for All Media versus Selected Media; done means these options appear whenever Compare Mode is not Off.

Written by the indexing model from the issue text.