Windows: drag-in install with a per-game d4r.ini

Players extract one ZIP into the game folder, copy their two NVIDIA
DLLs, and start the game from Steam, Epic or a shortcut. No launcher
script is needed; settings live in d4r\d4r.ini.

- Shim player mode: when the launcher has not set D4R_HIP_ROOT and
  d4r.ini sits beside the shim, derive the backend environment from it.
  Codegen flags stay at the Windows-validated values. NVIDIA DLLs must
  match an exact SHA256 in dll-pins.txt, with "you have X, you need Y"
  errors. Rejects a vkd3d/Wine d3d12.dll and code objects built for
  another GPU. [DLSS] Model accepts K or M and is applied by rewriting
  the render preset hints.

- d4r.ini exposes only options that exist on Windows: Model, AsyncInterop,
  ValidateOutput, Log, CacheDir. Invalid values fall back with a note in
  d4r_nvngx.log.

- d4r_nvngx_loader: one _nvngx.dll for all GPUs. It matches the game's
  adapter by LUID and loads _nvngx_<arch>.dll from the same folder.

- OptiScaler patch 0006: relative NvngxPath/NvngxDlssPath/
  NvngxFeaturePath resolve against OptiScaler's folder.

- package-windows-release.ps1 builds the release from the per-target
  game packages and refuses mixed targets or differing shared runtimes.

- Tests: test-player-config.ps1 (ini and DLL-pin decisions, loader
  selection on the local GPU) and test-windows-release-package.ps1.

patches/optiscaler/0006-relative-d4r-library-paths.patch

@@ -0,0 +1,30 @@
+Subject: [PATCH] Resolve relative d4r library paths against the OptiScaler folder
+
+Lets a drag-in d4r install ship OptiScaler.ini with NvngxPath=d4r instead of
+an absolute path that only an installer could know. Absolute paths behave
+exactly as before.
+---
+diff --git a/OptiScaler/Config.cpp b/OptiScaler/Config.cpp
+--- a/OptiScaler/Config.cpp
++++ b/OptiScaler/Config.cpp
+@@ -787,9 +787,17 @@
+         {
+             MainDllPath.set_from_config(readWString("Libraries", "OptiDllPath"));
+ 
+-            NvngxPath.set_from_config(readWString("Libraries", "NvngxPath"));
+-            NVNGX_DLSS_Library.set_from_config(readWString("Libraries", "NvngxDlssPath"));
+-            DLSSFeaturePath.set_from_config(readWString("Libraries", "NvngxFeaturePath"));
++            // A relative library folder (d4r drag-in installs use "d4r") is resolved
++            // against this DLL's folder, as LogFileName is. Absolute paths are unchanged.
++            auto libraryPath = [](std::optional<std::wstring> value) -> std::optional<std::wstring>
++            {
++                if (!value.has_value() || value->empty() || std::filesystem::path(*value).is_absolute())
++                    return value;
++                return (Util::DllPath().parent_path() / *value).lexically_normal().wstring();
++            };
++            NvngxPath.set_from_config(libraryPath(readWString("Libraries", "NvngxPath")));
++            NVNGX_DLSS_Library.set_from_config(libraryPath(readWString("Libraries", "NvngxDlssPath")));
++            DLSSFeaturePath.set_from_config(libraryPath(readWString("Libraries", "NvngxFeaturePath")));
+             NvapiDllPath.set_from_config(readWString("Libraries", "NvapiPath"));
+ 
+             FfxDx12Path.set_from_config(readWString("Libraries", "FfxDx12Path"));