Add asset, resource system, mesh formats, color, SDL3 display and example game

Asset directory with CMake add_asset (extension dispatched), plain file asset
access, resource/resource manager with async load thread and text loader,
URI utilities, mesh format helpers, generated color header, and example game
hooks wired through the engine.

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

tools/run_python/CMakeLists.txt

@@ -0,0 +1,14 @@
+# Copyright (c) 2026 Dominic Masters
+#
+# This software is released under the MIT License.
+# https://opensource.org/licenses/MIT
+
+function(dusk_run_python CMAKE_TARGET_NAME PYTHON_MODULE)
+  find_package(Python3 COMPONENTS Interpreter REQUIRED)
+
+  add_custom_target(${CMAKE_TARGET_NAME} ALL
+    WORKING_DIRECTORY ${DUSK_ROOT_DIR}
+    COMMAND
+      ${Python3_EXECUTABLE} -m ${PYTHON_MODULE} ${ARGN}
+  )
+endfunction()