docs: add compositor setup section and screenshot placeholder

README.md

@@ -2,9 +2,7 @@
 
 A lightweight, GPU-accelerated command palette for Linux (Wayland/X11). Zero Electron — every pixel rendered via WGPU. Async search that never blocks the UI.
 
-```
+![k-launcher](docs/screenshot.png)
-[screenshot placeholder]
-```
 
 ## Quick Start
 
@@ -24,6 +22,23 @@ cargo build --release
 | `Enter`   | Launch selected |
 | `Escape`  | Close           |
 
+## Compositor Setup
+
+k-launcher uses a normal window; configure your compositor to float it.
+
+**Hyprland** (`~/.config/hypr/hyprland.conf`):
+```
+windowrule = float, ^(k-launcher)$
+windowrule = center, ^(k-launcher)$
+bind = SUPER, Space, exec, k-launcher
+```
+
+**Sway** (`~/.config/sway/config`):
+```
+for_window [app_id="k-launcher"] floating enable, move position center
+bindsym Mod4+space exec k-launcher
+```
+
 ## Built-in Plugins
 
 | Trigger           | Plugin | Example        |