hud: header comment

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/mods/hud.cpp

@@ -1,9 +1,10 @@
 // HUD layout for widened views.
 //
 // The UI is laid out for 1024x768 and drawn into the top-left of the widened
-// render target. Selected windows are moved as a whole:
-//   - cUI_Taskbar2 (orbs, belt, skills at the bottom): centred horizontally
+// render target. Windows are moved as a whole:
 //   - cUI_Mercenary (party panel: portrait and health at the top): right edge
+//   - everything else (bottom bar, dialogs, inventory, maps, ...): centred
+// See docs/hud.md for the hooks and what happens outside a window's scope.
 //
 // A window is moved by transforming what it draws and what it receives, so
 // positions it computes itself (e.g. the potion arc) follow as well: