Cockpit surround: composite the gauges around the 3D view (default desktop layout)

Under BT_DEV_GAUGES the DEFAULT is now the pod-faithful cockpit surround: the 3D
world CENTERED with the six gauge surfaces composited AROUND it in the single main
window at 1/2 native scale, plus clickable RIO button lamps. Iterated as a visual
reference with the user, then landed in the engine.

- L4VB16.cpp/.h: BTCockpitLayout + BTCockpitComputeLayout (layout single source of
  truth, computed from the backbuffer canvas); BTDrawCockpitPanels (band fill ->
  button lamp quads -> 9-entry surface loop, phosphor-green mono / amber palette
  sec, Eng-sibling slot map -> GDI-atlas flight labels; D3DSBT_ALL state-block
  isolation = the floating-rocks trap); BTCockpitMouseDown/Up (client->bb hit-test
  + glass press/release/right-latch contract); BTApplyWorldViewport + DevGaugeDocked
  cockpit branches; shared BTLampBrightnessOf inline. Hooked at the top of
  BTDrawGaugeInset (before BT_SHOT, so shots include it).
- btl4main.cpp: glass preset (cockpit default, per-display panels opt-in); mode
  resolution -> gBTGaugeCockpit with work-area-clamped window sizing (-res = view
  size); WndProc WM_L/RBUTTON routing.
- L4VIDEO.cpp: BTWorldAspectOf cockpit branch (view rect on-screen aspect).
- L4VIDRND.cpp: CameraShipHUDRenderable::Render made viewport-relative.

Buttons = the L4GLASSWIN address banks x0.5 (Heat 0x2F, Mfd2 0x27, Comm 0x37, Mfd1
0x0F, Mfd3 0x07 red; radar rails 0x10-0x1B yellow; flight 0x38-0x47 blue, labeled).
Full rect is the hit target; the surface draws over it so only the lamp edge shows.
Precedence: BT_GLASS_PANELS=1 stands cockpit down > BT_COCKPIT=1 > _WINDOW/_DOCK
opt-out > cockpit default; BT_COCKPIT=0 = dock-bottom. Green tunable via
BT_COCKPIT_TINT. Renders in ALL builds; only the PadRIO click/lamp seam is
BT_GLASS-gated.

Verified (awaiting playtest): both build/ + build-glass/ compile (0 error C);
glass BT_SHOT matches the mockup; 500-click storm during a live mission survived
(Gitea #18 Receiver-gap fix holds); BT_COCKPIT=0 dock-bottom unregressed;
BT_GLASS_PANELS=1 stands cockpit down; pod build renders the panels.

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

engine/MUNGA_L4/L4VIDEO.cpp

@@ -6,6 +6,7 @@
 #include "..\munga\eyecandy.h"
 #include "l4vidrnd.h"
 #include "l4video.h"
+#include "l4vb16.h"		// BTCockpitLayout / BTCockpitComputeLayout (cockpit aspect)
 #include "..\munga\matrix.h"
 #include "..\munga\mover.h"
 #include "..\munga\jmover.h"
@@ -9384,6 +9385,22 @@ static float BTWorldAspectOf(int client_w, int client_h)
 {
 	extern int gBTGaugeDockBottom;
 	extern int BTGaugeStripHeightFor(int width);
+	// COCKPIT: the world occupies the CENTERED view sub-rect of the fixed-size
+	// backbuffer (canvas), which D3D stretches into the client area.  The view's
+	// ON-SCREEN aspect = (viewW/canvasW * client_w) / (viewH/canvasH * client_h).
+	extern int gBTGaugeCockpit;
+	extern int gBTCockpitCanvasW, gBTCockpitCanvasH;
+	if (gBTGaugeCockpit && gBTCockpitCanvasW > 0 && gBTCockpitCanvasH > 0)
+	{
+		BTCockpitLayout L;
+		BTCockpitComputeLayout(gBTCockpitCanvasW, gBTCockpitCanvasH, &L);
+		if (L.viewW > 0 && L.viewH > 0)
+		{
+			float w = (float)L.viewW * (float)client_w / (float)gBTCockpitCanvasW;
+			float h = (float)L.viewH * (float)client_h / (float)gBTCockpitCanvasH;
+			if (h > 0.0f) return w / h;
+		}
+	}
 	float world_h = (float)client_h;
 	if (gBTGaugeDockBottom)
 	{