Finish wiring up the TagOverlay

We had to fix a couple of compile errors that weren't showing while it
wasn't wired up (since I never just tried to compile TagOverlay.zig on
its own). We also changed the lifecycle to re-create/destroy the surface
to show/hide it, similar to the way that river-tag-overlay actually did
it.

Finally, I added @branchHint(.cold) to a few places in the event loop
where, if we're in the branch, the wm is definitely exiting, so it's
fine if they're cold (should almost never happen).

src/Config.zig

@@ -117,8 +117,8 @@ pub const TagOverlayConfig = struct {
     pub fn toTagOverlayOptions(self: TagOverlayConfig) TagOverlay.Options {
         return .{
             .border_width = self.border_width,
-            .tag_amount = @intCast(std.math.clamp(@as(u32, self.tag_amount), 1, 32) - 1),
-            .tags_per_row = @intCast(std.math.clamp(@as(u32, self.tags_per_row), 1, 32) - 1),
+            .tag_amount = @intCast(std.math.clamp(@as(u32, self.tag_amount), 1, 32)),
+            .tags_per_row = @intCast(std.math.clamp(@as(u32, self.tags_per_row), 1, 32)),
             .square_size = self.square_size,
             .square_inner_padding = self.square_inner_padding,
             .square_padding = self.square_padding,