Glass cockpit: per-display windows (BT_GLASS_PANELS)

Break the desktop glass cockpit's secondary displays out of the single
combined pad panel + D3D gauge strip into ONE window per pod display, each
carrying that display's surface with its RIO button bank, arranged
pod-faithfully around the main view.  New TU engine/MUNGA_L4/L4GLASSWIN.*
(BT_GLASS-only), selected by the -platform glass preset via the new runtime
gate BT_GLASS_PANELS (=0 falls back to the legacy single panel + dock).

- Surfaces are CPU-expanded from the shared gauge buffer
  (SVGA16::ExpandPlaneToBGRA, no D3D) and StretchDIBits'd in -- the D3D
  dev-composite path (dock / window / overlay) stands down while active.
- Buttons sit UNDER the imagery: big hidden click targets that reach into
  the display, with only a small protruding edge showing as a lamp light.
  Red MFD banks tile the top/bottom; radar rails run the sides + a bottom
  row; a Flight Controls window hosts the no-display banks.
- Windows: Heat / Engineering / Comm / Left Weapons / Right Weapons / radar
  + Flight Controls; edge-to-edge (no in-client margin/title; OS caption
  labels each).
- Fix blank surfaces: application/ghWnd are duplicate-defined and bind
  non-deterministically under /FORCE, so the fresh L4GLASSWIN TU read NULL.
  Reach the renderer/window via BTResolveGaugeRenderer/BTResolveMainWindow
  defined in btl4main.cpp off the real btl4App/hWnd pointers.  New gotcha:
  reconstruction-gotchas.md S6 duplicate-GLOBAL corollary.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

engine/MUNGA_L4/L4VB16.h

@@ -7,6 +7,15 @@
 
 
 class L4graphicsPort;
+class GaugeRenderer;
+
+// GLASS: resolve the gauge renderer / main window.  DEFINED in game/btl4main.cpp
+// off the REAL app + window pointers it holds as locals -- NOT off the
+// `application`/`ghWnd` globals, which are duplicate-defined and bind
+// non-deterministically per link under /FORCE (the "duplicate-symbol race" --
+// CMakeLists.txt:186), so a newly-added engine TU (L4GLASSWIN) can read NULL.
+GaugeRenderer *BTResolveGaugeRenderer();
+void          *BTResolveMainWindow();		// HWND (kept void* -- no windows.h dependency)
 
 //########################################################################
 //######################### Video16BitBuffered ###########################
@@ -306,6 +315,17 @@ public:
 	void DrawDevSurface(LPDIRECT3DDEVICE9 device, int slot, int mask, int paletteID,
 						int monoTint, float dstX, float dstY, float dstW, float dstH,
 						int rotateCCW = 0);
+
+	// GLASS (per-display windows, L4GLASSWIN): CPU-expand ONE gauge surface (a
+	// bit-plane of the shared pixelBuffer) into a 32-bit BGRA image for GDI
+	// StretchDIBits -- no D3D.  Same pixel rule as DrawDevSurface: monoTint < 0 ->
+	// palette-expand via palette[paletteID]; else fill (word & mask) ? monoTint : 0
+	// (monoTint is a 0x00RRGGBB value here, NOT R5G6B5).  rotateQuadrant: 0 = native
+	// (outW=bufW, outH=bufH); 1 = 90 CCW / 3 = 90 CW -> transposed (outW=bufH,
+	// outH=bufW), for the portrait secondary CRT.  `dst` must hold >= bufW*bufH
+	// dwords; the image is written TOP-DOWN.  *outW/*outH receive the produced size.
+	void ExpandPlaneToBGRA(int mask, int paletteID, int monoTint, int rotateQuadrant,
+						   unsigned long *dst, int *outW, int *outH);
 };
 
 //########################################################################