4.10 reconstruction: BTL4OPT.EXE links clean and BOOTS to the first staged brick

The reconstructed tree now produces a runnable binary with the authentic
1995 toolchain (BC4.52 / tlink32 / DPMI32):

- BTL4.CPP main TU reconstructed from the 4.11 Ghidra decomp (FUN_0040109c)
  + the 4.10 binary's own string pool + surviving RPL4TOOL.CPP house style;
  probe_main.cpp scaffold retired (BTL4.NOTES.md documents every decoded call)
- L4NET.CPP staged: L4NetworkManager ctor/dtor + 10 vtable-pulled virtuals
  (standalone-benign ones no-op, network ones Fail loudly) + NetNub client
  globals (Net_Common_Ptr=NULL routes L4File to its plain-DOS path)
- build410.sh: libs now built in the AUTHENTIC makefile member order
  (MUNGA.MAK / mungal4.mak / BT.MAK / BTL4.MAK). Order is load-bearing:
  tlink emits static-init records in module pull order, and alphabetical
  order booted into a null-vptr crash (IcomManager::ClassDerivations
  constructing before parent NetworkClient::ClassDerivations). Also fixed
  stage_link to the proven 32-bit lib set (SOSDBXC+SOSMBXC, no WATTCPLG)
- BOXTREE.HPP MemoryBlock unify, BTL4GRND notify stubs, remaining engine
  backfills (audio/gauge/resource/stream TUs) that closed the deep ledger

Smoke test (DOSBox-X + 32RTM, copy of the pod BT tree, our exe swapped in):
  BattleTech v4.10
  BTL4Application::BTL4Application
  l4net.cpp(22): L4NetworkManager -- l4net.cpp not yet reconstructed
Static init, main, -egg parse, BTL4.RES load (version 1.0.6 check passes),
ApplicationManager and the BTL4Application ctor chain all execute real
reconstructed code; boot halts at the first staged Fail() as designed.
Next brick: the real l4net.cpp body.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

restoration/source410/BT_L4/BTL4MPPR.CPP

@@ -40,3 +40,80 @@ MechRIOMapper::SharedData
 		Subsystem::AttributeIndex,
 		1
 	);
+
+Derivation
+	L4MechControlsMapper::ClassDerivations(
+		MechControlsMapper::ClassDerivations,
+		"L4MechControlsMapper"
+	);
+
+L4MechControlsMapper::SharedData
+	L4MechControlsMapper::DefaultData(
+		L4MechControlsMapper::ClassDerivations,
+		Subsystem::MessageHandlers,
+		Subsystem::AttributeIndex,
+		1
+	);
+
+L4MechControlsMapper::L4MechControlsMapper(
+	Mech						*owner,
+	int							subsystem_ID,
+	CString						subsystem_name,
+	RegisteredClass::ClassID	class_ID,
+	SharedData					&shared_data
+):
+	MechControlsMapper(owner, subsystem_ID, subsystem_name, class_ID, shared_data)
+{
+}
+
+L4MechControlsMapper::~L4MechControlsMapper()
+{
+}
+
+Logical
+	L4MechControlsMapper::TestInstance() const
+{
+	return IsDerivedFrom(ClassDerivations);
+}
+
+MechThrustmasterMapper::MechThrustmasterMapper(
+	Mech						*owner,
+	int							subsystem_ID,
+	CString						subsystem_name,
+	RegisteredClass::ClassID	class_ID,
+	SharedData					&shared_data
+):
+	L4MechControlsMapper(owner, subsystem_ID, subsystem_name, class_ID, shared_data)
+{
+}
+
+MechThrustmasterMapper::~MechThrustmasterMapper()
+{
+}
+
+Logical
+	MechThrustmasterMapper::TestInstance() const
+{
+	return IsDerivedFrom(ClassDerivations);
+}
+
+MechRIOMapper::MechRIOMapper(
+	Mech						*owner,
+	int							subsystem_ID,
+	CString						subsystem_name,
+	RegisteredClass::ClassID	class_ID,
+	SharedData					&shared_data
+):
+	L4MechControlsMapper(owner, subsystem_ID, subsystem_name, class_ID, shared_data)
+{
+}
+
+MechRIOMapper::~MechRIOMapper()
+{
+}
+
+Logical
+	MechRIOMapper::TestInstance() const
+{
+	return IsDerivedFrom(ClassDerivations);
+}