Fix the size caluation for left-right windows used to spread out cells horizontally evenly. From Michael Grant in GitHub issue 4724.

usr.bin/tmux/layout.c

···
-/* $OpenBSD: layout.c,v 1.52 2024/12/17 08:40:24 nicm Exp $ */
+/* $OpenBSD: layout.c,v 1.53 2025/12/03 07:35:32 nicm Exp $ */
 
 /*
  * Copyright (c) 2009 Nicholas Marriott <[e-mail]>
···
 layout_spread_cell(struct window *w, struct layout_cell *parent)
 {
 	struct layout_cell	*lc;
-	struct style		*sb_style = &w->active->scrollbar_style;
 	u_int			 number, each, size, this, remainder;
-	int			 change, changed, status, scrollbars;
+	int			 change, changed, status;
 
 	number = 0;
 	TAILQ_FOREACH (lc, &parent->cells, entry)
···
 	if (number <= 1)
 		return (0);
 	status = options_get_number(w->options, "pane-border-status");
-	scrollbars = options_get_number(w->options, "pane-scrollbars");
 
-	if (parent->type == LAYOUT_LEFTRIGHT) {
-		if (scrollbars)
-			size = parent->sx - sb_style->width + sb_style->pad;
-		else
-			size = parent->sx;
-	}
+	if (parent->type == LAYOUT_LEFTRIGHT)
+		size = parent->sx;
 	else if (parent->type == LAYOUT_TOPBOTTOM) {
 		if (layout_add_horizontal_border(w, parent, status))
 			size = parent->sy - 1;