V120 QUICK FF ARROW SCROLL NO-REOPEN FIX

Base
- Built from v119.

What changed
- Arrow-key movement in the Quick finite-fault editor no longer destroys and recreates the editor window.
- The visible 5x5 viewport is updated in-place: column labels, row labels, cell text, and colors are rewritten without reopening the tool window.

Why
- The old behavior called quick_ff_reopen_editor() on every arrow-key press. Windows then placed the recreated tool window at a new default position, so the editor flashed and appeared to move diagonally.
