Map: zoomed-view symbols centred, 10x reveal and enemy range; progress screen on the menu background

- Megamap / TAB map zoomed view: heroes' markers and the other symbols
  (integer 200h centre immediates) follow the view's centre.
- Map reveal: the hero's reveal stamp scaled 10x (mods/mapreveal.cpp,
  docs/map-reveal.md); creatures on the zoomed map shown within 10x the
  sight range.
- Load / save progress screen drawn on the rock background across the full
  width, the picture blended over it (mods/loadingscreen.cpp); the classic
  1024x768 frame is gone.

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

src/mods/hud.cpp

@@ -66,7 +66,7 @@ int OffsetFor(Anchor anchor) {
     // The main menu's frame shifts the windows in it; over a 16:9 screen
     // (no frame) dialogs are centred like in a game (user, 2026-10-21).
     const bool inMenuFrame = mods::widescreen::MenuIsShowing() && g_menuFrameDx != 0;
-    if (!enabled || width <= kLayoutWidth || mods::widescreen::IsClassicFrame() || inMenuFrame ||
+    if (!enabled || width <= kLayoutWidth || mods::widescreen::IsLoadingScreen() || inMenuFrame ||
         anchor == Anchor::Screen) {
         return 0;
     }