compositor+matugen: border override, hypr/mango layout overrides, new

templates, respect XDG paths
- Add Hyprland and MangoWC templates
- Add GUI gaps, window radius, and border thickness overrides for niri,
  Hyprland, and MangoWC
- Add replacement support in matugen templates for DATA_DIR, CACHE_DIR,
  CONFIG_DIR
fixes #1274
fixes #1273

core/internal/config/embedded/hypr-layout.conf

@@ -0,0 +1,11 @@
+# Auto-generated by DMS - do not edit manually
+
+general {
+    gaps_in = 4
+    gaps_out = 4
+    border_size = 2
+}
+
+decoration {
+    rounding = 12
+}