patch 9.2.0530: WinBar row vertical separator not refreshed on window change

patch 9.2.0530: WinBar row vertical separator not refreshed on window change

Problem:  After the current window changes, the vertical separator cell
          on the WinBar row keeps its previous VertSplit / VertSplitNC
          highlight.  Content rows and status line rows of the same
          window are refreshed correctly; only the WinBar row is left
          behind, so the WinBar's separator no longer matches the
          surrounding cells (Mao-Yining)
Solution: Include the WinBar row in draw_vsep_win() when redrawing
          from the top of the window.  When called with row == 0 the
          loop now starts at wp->w_winrow (the WinBar row when present)
          instead of W_WINROW(wp) (the content start), so the separator
          highlight on the WinBar row is updated together with the rest
          of the window (Hirohito Higashi).

fixes:  #20304
closes: #20310

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Signed-off-by: Hirohito Higashi <h.east.727@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>