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>

docs/screens.md

@@ -88,3 +88,21 @@ window's own pictures removed.
   offset 0 while the menu showed. Now only while the menu frame is drawn
   centred (it shifts the windows itself); otherwise dialogs are centred and
   their full-layout dimming stretched, as in a game.
+
+## Load / save progress screen (2026-10-25)
+
+Request: the progress screen shown while loading / saving should use the
+menu screens' background. The game's screen (`DxDriver7::LoadingScreen`
+`0x6469d0`, thiscall (progress, text)) draws with GDI into the back buffer's
+DC (surface +0xbc, GetDC vf 0x44 / ReleaseDC vf 0x68): the 1024x768 picture
+(HBITMAP +0x200) at 0, 0, the bar (+0x204 / +0x208) and the text at y 700,
+then Flip; it redraws only when the bar moves. Until now it was presented as
+a 1024x768 "classic" frame scaled to the monitor.
+
+`mods/loadingscreen.cpp`: before the game's drawing, `DrawBackground` across
+the whole render width in a scene of its own (`DxDriver7` BeginScene
+`0x646f50` / EndScene `0x646fd0`); the game's GDI drawing is moved to the
+centred 1024 frame with `SetViewportOrgEx` on the back buffer's DC, caught in
+`CreateCompatibleDC(hdc)` which the game calls right after getting it. Every
+frame is now presented at the full render width (borderless.cpp has one
+layout).