Reserve the top of every monitor for the bar

edge::spacer: a full-width, empty, click-through Background layer as tall
as the pills reach (TOP_GAP + COMPACT_H = 44 px) with Zone::Reserve.
Hyprland keeps tiled and maximised windows below it and lets fullscreen
windows cover it, so space is reserved exactly where the bar stays.
Verified: reserved 0 44 0 0 on all monitors, a tiled window moved from
y=636 to 680, a fullscreen one still covers 1920x1080, idle 0 frames.

src/edge.rs

@@ -410,3 +410,22 @@ pub fn view(monitor: &Monitor) -> LayerWindow {
 
     window.child(Rectangle::new().width(Parent).height(Parent).on_hover(at_edge(monitor.name.clone())))
 }
+
+/*
+ * keeps windows out from under the bar: an empty strip as tall as the pills reach,
+ * reserving its height on every monitor. Hyprland lets tiled and maximised windows
+ * respect it and fullscreen ones cover it, which is just when the bar stays and when
+ * it hides; it goes with the shell. the bar's own windows ignore what's reserved, so
+ * they stay at the top edge. reads nothing, so it never redraws
+ */
+pub fn spacer(_: &Monitor) -> LayerWindow {
+    LayerWindow::new()
+        .width(Full)
+        .height(TOP_GAP + COMPACT_H)
+        .anchor_vertical(Vertical::Top)
+        .layer(Layer::Background)
+        .space(Zone::Reserve)
+        .namespace("magic-reserve")
+        .click_through()
+        .child(Rectangle::new().width(0.0).height(0.0))
+}

src/main.rs

@@ -28,6 +28,7 @@ fn main() {
         .ipc("island", island::command)
         .ipc("control", control::command)
         .ipc("tray", tray::command)
+        .window_per_monitor(edge::spacer)
         .window_per_monitor(edge::view)
         .window_per_monitor(island::view)
         .window_per_monitor(workspaces::view)