Quest book map tab: keep the cursor visible

The zoomed map view resets the viewport to the full render size when done;
the HUD layer shifted that reset past the render target, SetViewport failed
and the map's 256x256 viewport stayed set, clipping the cursor. Full-width
viewports at x 0 are no longer shifted.

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

src/mods/hud.cpp

@@ -402,8 +402,13 @@ using ClearFn = HRESULT(__stdcall*)(void* device, DWORD count, Rect7* rects, DWO
 SetViewportFn g_setViewport = nullptr;
 ClearFn g_clear = nullptr;
 
+// A viewport across the whole render width is a reset, not one of the window's
+// own (e.g. the zoomed map view in the quest book restores it with 0x646510
+// when done): shifted, it would reach past the render target, SetViewport
+// fails and the window's small viewport stays set, clipping the cursor.
 HRESULT __stdcall SetViewportShifted(void* device, Viewport7* viewport) {
-    if (g_offsetX == 0 || !viewport) {
+    if (g_offsetX == 0 || !viewport ||
+        (viewport->x == 0 && static_cast<int>(viewport->width) >= mods::widescreen::RenderWidth())) {
         return g_setViewport(device, viewport);
     }
     Viewport7 shifted = *viewport;