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/backdate.py

@@ -75,7 +75,7 @@ def main():
         line = re.sub(r"(?<![:\w])GetMessageHandlers\(\)", "MessageHandlers", line)
         line = re.sub(r"(?<![:\w])GetAttributeIndex\(\)", "AttributeIndex", line)
         line = line.replace("PostQuitMessage(AbortExitCodeID);", 'Fail("Exiting");')
-        for bad in ("atlbase.h", "windows.h", "winsock"):
+        for bad in ("atlbase.h", "windows.h", "winsock", "windows.hpp", "<cstdlib>", "<cstring>", "<cstdio>"):
             if bad in line and "#include" in line:
                 line = ""
                 break