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/MODE.cpp

@@ -0,0 +1,59 @@
+#include "munga.h"
+#pragma hdrstop
+
+#include "mode.h"
+
+#if defined(DEBUG)
+#	define Test_Tell(n) DEBUG_STREAM << n
+#else
+#	define Test_Tell(n)
+#endif
+
+//############################################################################
+//############################    ModeManager    #############################
+//############################################################################
+ModeManager::ModeManager(ModeMask initial_mask)
+{
+	Check_Pointer(this);
+
+	modeMask = initial_mask;
+
+	Check_Fpu();
+}
+
+ModeManager::~ModeManager()
+{
+	Check(this);
+	Check_Fpu();
+}
+
+Logical
+	ModeManager::TestInstance() const
+{
+	Check_Fpu();
+	return True;
+}
+
+Logical
+	ModeManager::ModeStringLookup(
+		const char *name,
+		ModeMask *returned_value
+	)
+{
+	Check(this);
+
+	// There's only one mode value available at this level.
+
+	if (stricmp(name, "ModeAlwaysActive") == 0)
+	{
+		*returned_value = ModeManager::ModeAlwaysActive;
+		Check_Fpu();
+		return True;
+	}
+	else
+	{
+		*returned_value = (ModeMask) 0;
+	}
+	Check_Fpu();
+	return False;
+}