Initial commit: bt411 -- standalone Windows BattleTech (Tesla 4.10 port)

Clean, self-contained extraction of the BattleTech-specific work from the
reverse-engineering workspace -- engine + game + content + build, with nothing
from Red Planet or the raw archive dumps. Builds green (Win32) and runs the
single-player drive->animate->target->fire->damage->destroy loop out of the box.

Layout:
  engine/   MUNGA + MUNGA_L4 shared 2007 engine, carrying our BT render/loader
            work (bgfload/L4D3D/L4VIDEO: BSL bit-slice decode, LOD/ground/shadow
            models) + image codec; the minimal rp/ headers the audio HAL needs
  game/     reconstructed BT logic + surviving-original BT source + fwd shims
            + WinMain launcher
  content/  full runtime tree (BTL4.RES, VIDEO/, GAUGE/, AUDIO/, eggs, BTDPL.INI)
  docs/     format specs + reconstruction ledgers
  reference/ raw Ghidra pseudocode (recon source-of-truth) + decomp exporter
  tools/    MP console emulator + map/resource scanners

One top-level CMake builds munga_engine lib + bt410_l4 game lib + btl4.exe.
All paths relativized (186 fwd shims + ~437 CMake abs paths -> repo-relative);
DXSDK is the one external, overridable via -DDXSDK. Verified: builds to a
byte-identical 2.27MB exe and runs combat (TARGET DESTROYED, 0 crashes) against
the bundled content.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

engine/MUNGA/RECT2D.cpp

@@ -0,0 +1,138 @@
+#include "munga.h"
+#pragma hdrstop
+
+#include "rect2d.h"
+
+//
+//------------------------------------------------------------------------
+// Creators
+//------------------------------------------------------------------------
+//
+Rectangle2D::Rectangle2D()
+{
+	MakeEmpty();				// uninitialized rectangles should be "empty"
+}
+
+Rectangle2D::Rectangle2D(
+		Vector2DOf<int> bl,
+		Vector2DOf<int> tr
+	)
+{
+	bottomLeft = bl;
+	topRight = tr;
+}
+
+Rectangle2D::Rectangle2D(
+		int x1, int y1, int x2, int y2
+	)
+{
+	bottomLeft.x = x1;
+	bottomLeft.y = y1;
+	topRight.x = x2;
+	topRight.y = y2;
+}
+
+//
+//------------------------------------------------------------------------
+// Union (returns bounding rectangle)
+//------------------------------------------------------------------------
+//
+void
+	Rectangle2D::Union(
+			const Rectangle2D& r1,
+			const Rectangle2D& r2
+		)
+{
+	Check(this);
+	Check(&r1);
+	Check(&r2);
+
+	if (r1.IsEmpty())
+	{
+		if (r2.IsEmpty())
+		{
+			MakeEmpty();
+		}
+		else
+		{
+			bottomLeft = r2.bottomLeft;
+			topRight = r2.topRight;
+		}
+	}
+	else
+	{
+		if (r2.IsEmpty())
+		{
+			bottomLeft = r1.bottomLeft;
+			topRight = r1.topRight;
+		}
+		else
+		{
+			bottomLeft.x = Min(r1.bottomLeft.x, r2.bottomLeft.x);
+			bottomLeft.y = Min(r1.bottomLeft.y, r2.bottomLeft.y);
+			topRight.x = Max(r1.topRight.x, r2.topRight.x);
+			topRight.y = Max(r1.topRight.y, r2.topRight.y);
+		}
+	}
+}
+
+//
+//------------------------------------------------------------------------
+// Intersection (returns overlapping section)
+//------------------------------------------------------------------------
+//
+void
+	Rectangle2D::Intersection(
+		const Rectangle2D& r1,
+		const Rectangle2D& r2
+		)
+{
+	Check(this);
+	Check(&r1);
+	Check(&r2);
+
+	if (r1.IsEmpty())
+	{
+		MakeEmpty();
+	}
+	else
+	{
+		if (r2.IsEmpty())
+		{
+			MakeEmpty();
+		}
+		else
+		{
+			bottomLeft.x = Max(r1.bottomLeft.x, r2.bottomLeft.x);
+			bottomLeft.y = Max(r1.bottomLeft.y, r2.bottomLeft.y);
+			topRight.x = Min(r1.topRight.x, r2.topRight.x);
+			topRight.y = Min(r1.topRight.y, r2.topRight.y);
+		}
+	}
+}
+
+//
+//------------------------------------------------------------------------
+// Output stream operator
+//------------------------------------------------------------------------
+//
+std::ostream& operator<<(std::ostream& Stream, const Rectangle2D& r)
+{
+	Check(&r);
+	return Stream << '(' << r.bottomLeft << ',' << r.topRight << ')';
+}
+
+//
+//------------------------------------------------------------------------
+// TestInstance
+//------------------------------------------------------------------------
+//
+Logical
+	Rectangle2D::TestInstance() const
+{
+	return True;
+}
+
+#if defined(TEST_CLASS)
+#	include "rect2d.tcp"
+#endif