fix(statuscolumn): force full redraw when signcolumn is invalid

Fix #24655

src/nvim/drawscreen.c

@@ -595,6 +595,8 @@ int update_screen(void)
     // Reset 'statuscolumn' if there is no dedicated signcolumn but it is invalid.
     if (*wp->w_p_stc != NUL && !wp->w_buffer->b_signcols.valid && win_no_signcol(wp)) {
       wp->w_nrwidth_line_count = 0;
+      wp->w_valid &= ~VALID_WCOL;
+      wp->w_redr_type = UPD_NOT_VALID;
     }
   }
 

test/functional/ui/statuscolumn_spec.lua

@@ -727,6 +727,8 @@ describe('statuscolumn', function()
         end
         return vim.v.lnum .. '%=' .. sign
       end
+      vim.o.number = true
+      vim.o.numberwidth = 2
       vim.o.statuscolumn = "%!v:lua.StatusCol()"
     ]])
     command('sign place 1 line=2 name=sign')