Add fresh CMake/platform scaffolding, core engine, and SDL3 window

Platform folders, cmake target/option/platform detection, Linux and PSP
scripts and Docker setup, assert/util/thread/error/log/perf/time/console/
engine/display modules, and an SDL3 window cleared to red.

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

cmake/windows/target.cmake

@@ -0,0 +1,21 @@
+# Copyright (c) 2026 Dominic Masters
+#
+# This software is released under the MIT License.
+# https://opensource.org/licenses/MIT
+
+# Platform setup for the windows target, included by the root CMakeLists.txt.
+# Only sets defaults and definitions; the root applies them.
+
+# Source directories to build for this platform.
+set(DUSK_PLATFORM_DIRS duskwindows dusksdl3 duskvulkan)
+
+# Default values for the shared options declared in the root CMakeLists.txt.
+set(DUSK_DEFAULT_ASSERTIONS_FAKED OFF)
+set(DUSK_DEFAULT_BACKTRACE OFF)
+set(DUSK_DEFAULT_TRACK_MEMORY ON)
+
+# Platform definitions.
+set(DUSK_PLATFORM_DEFINITIONS
+  DUSK_PLATFORM_ENDIAN_LITTLE
+  DUSK_WINDOWS
+)