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>

context/gauges-hud.md

@@ -72,11 +72,40 @@ TestInstance/BecameActive/Execute. **Gotchas that bite EVERY widget:**
   (`RecomputeCondenserValves`, FUN_0049f788, was a no-op stub). [T2]
 
 ## Dev composite (off-pod)
-`BT_DEV_GAUGES` renders the 6 pod [[MFD]] surfaces in a separate 960×384 window (bit-plane masks
-over one shared `SVGA16` pixelBuffer; `SVGA16::DrawDevSurface`). On the POD they come from
-`SETENV.BAT`/`L4GAUGE` on the real multi-adapter hardware (`FindBestAdapterIndices`/`BuildWindows`,
-intact). The `overlay` port (SectorDisplay lives there) shares the `sec` physical surface via a
-different bit-plane (0x00C0). [T2]
+`BT_DEV_GAUGES` renders the 6 pod [[MFD]] surfaces (bit-plane masks over one shared `SVGA16`
+pixelBuffer; `SVGA16::DrawDevSurface`). On the POD they come from `SETENV.BAT`/`L4GAUGE` on the
+real multi-adapter hardware (`FindBestAdapterIndices`/`BuildWindows`, intact). The `overlay` port
+(SectorDisplay lives there) shares the `sec` physical surface via a different bit-plane (0x00C0). [T2]
+
+## Cockpit surround (the DEFAULT desktop layout, 2026-07-20) [T2]
+Under `BT_DEV_GAUGES`, the DEFAULT is now the **cockpit surround** (`L4VB16.cpp`
+`BTDrawCockpitPanels`): the 3D world view CENTERED with the six gauge surfaces composited AROUND
+it in the SINGLE main window at **½ native scale** (MFD 320×240, radar 240×320 portrait), plus
+clickable RIO button lamps — the pod-faithful arrangement (Coolant UL, Mfd2 upper-center, Comm/Hot
+Box UR, Mfd1/Mfd3 lower flanks, secondary/radar flush below). The pod monitors physically clip the
+eyeport, so the corner MFDs + top-center overlap the view edges. Mono MFDs are tinted **phosphor
+green** (radar keeps its **amber** palette); the world viewport is the centered view rect
+(`BTApplyWorldViewport` cockpit branch) so the reticle/HUD follow for free (dpl2d maps through the
+viewport), and `gWindowAspect` = the view rect's on-screen aspect (`BTWorldAspectOf` cockpit branch).
+- **Layout = single source of truth**: `BTCockpitLayout` / `BTCockpitComputeLayout(canvasW,canvasH)`
+  in `l4vb16.h`/`L4VB16.cpp`, computed FROM the backbuffer (canvas) size — consumed by the window
+  sizing (`btl4main.cpp`), the world viewport, the panel/button draw, the aspect, and the mouse
+  hit-test. Constants: `SCALE=0.5, OVL=44 (corner overlap), LAMP=16 (protruding lamp edge),
+  REDCELL=64 (hidden hit depth), RAILW=26`; `canvas = view + (552, 548)`.
+- **Buttons** = the L4GLASSWIN geometry ×0.5 with the same address banks (Heat 0x2F, Mfd2 0x27,
+  Comm 0x37, Mfd1 0x0F, Mfd3 0x07 red 8-btn; radar rails 0x10-0x15/0x18-0x1D + bottom
+  {0x16,0x17,0x1F,0x1E} yellow; flight 0x38-0x3F/0x40-0x47 blue, labeled). Full rect = hit target;
+  the surface draws OVER it so only the lamp edge shows (the PaintGlass painter trick). Mouse:
+  main WndProc `WM_L/RBUTTON` → `BTCockpitMouseDown/Up` (client→bb map, glass press/release/right-
+  latch contract) → `PadRIO::SetScreenButton` (`#ifdef BT_GLASS`; dim/no-op in pod builds). Lamp
+  brightness = `BTLampBrightnessOf` (shared inline in l4vb16.h) over `PadRIO::GetLampState`.
+- **Env / precedence** (resolved once in btl4main → `gBTGaugeCockpit`): `BT_GLASS_PANELS=1`
+  (Cyd's per-display windows) stands cockpit down > explicit `BT_COCKPIT=1` > `BT_DEV_GAUGES_WINDOW`
+  (separate window) / `BT_DEV_GAUGES_DOCK` (legacy inset) opt-out > **cockpit default**.
+  `BT_COCKPIT=0` forces the dock-bottom strip. `-res W H` = the WORLD VIEW size (canvas clamped to
+  the work area). Green tint tunable via `BT_COCKPIT_TINT=RRGGBB` (default `0x27E8`). Labels are a
+  lazy GDI-baked MANAGED atlas (survives device reset). Renders in ALL builds; only the PadRIO
+  click/lamp seam is BT_GLASS-gated. Full detail: `docs/GAUGE_COMPOSITE.md`.
 
 ## MP gauge-window FREEZE = dangling bindings + permanent SEH disable (Gitea #12, 2026-07-19) [T2 log-convicted]
 The live-MP "dev-gauges window froze entirely mid-session" incident (issue #12) is NOT a