Add the renderer process

The renderer becomes two programs: the adapter (t5deRenderEngine.dll, 32-bit, in IMVU's process) and a 64-bit renderer process (t5de-renderer.exe) drawing with Diligent Engine, fetched with FetchContent and pinned. For now a spike: the adapter starts the renderer process for each engine and signals each frame through a shared memory channel, and the renderer process draws a box into a child window in the client's 3D view.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

CLAUDE.md

@@ -1,7 +1,9 @@
 # t5de-renderer
 
-A renderer plugin for IMVU Classic (see README.md and docs/interface.md). Part of T5DE; the patches and the patcher
-are in the `t5de` repository (git.t5de.dev/t5de/t5de, usually checked out beside this one).
+A new renderer for IMVU Classic: a 32-bit adapter DLL the client loads as a renderer plugin, and a 64-bit renderer
+process drawing with Diligent Engine (see README.md, docs/architecture.md, docs/interface.md). Part of T5DE; the
+patches and the patcher are in the `t5de` repository (git.t5de.dev/t5de/t5de, usually checked out beside this one).
+The user chose this architecture for ray tracing, mesh shaders and a possible browser client later.
 
 ## Rules
 
@@ -13,9 +15,12 @@ are in the `t5de` repository (git.t5de.dev/t5de/t5de, usually checked out beside
 
 ## Notes
 
-- The plugin must match IMVU's ABI: 32-bit, MSVC (cl or clang-cl; MinGW's C++ ABI differs), `__thiscall`
-  virtual methods in IMVU's vtable order, Boost 1.61's `shared_ptr` layout. Exceptions must not cross into IMVU's
-  code (a different C runtime); the CRT is linked statically.
+- The adapter must match IMVU's ABI: 32-bit, MSVC (cl or clang-cl; MinGW's C++ ABI differs), `__thiscall`
+  virtual methods in IMVU's vtable order (never overloaded: MSVC orders overloads unlike their declaration), Boost
+  1.61's `shared_ptr` layout. Exceptions must not cross into IMVU's code (a different C runtime); the CRT is linked
+  statically. Code shared with the 64-bit renderer process (`include/t5de/protocol/`) uses fixed-size fields only.
+- The development VM has no graphics driver (Microsoft Basic Render Driver): Direct3D 11 works in software, IMVU's
+  OpenGL renderer doesn't, and performance there means nothing.
 - Ghidra 12.2 (Java 25) is at `%LOCALAPPDATA%\Programs\ghidra_12.2_PUBLIC`; projects in
   `%LOCALAPPDATA%\t5de-dev\ghidra`, analysed headless (`support\analyzeHeadless.bat`). The client to analyse is the
   `t5de` checkout's `.cache/<version>/install`.