fix the clang CI build

Every module unit now includes the standard headers it uses. Declarations
reaching a unit only through an imported module's global module fragment
are reachable but not visible, so ADL misses the free operators older
libstdc++ declares beside a type - reproduced on ubuntu 24.04 (libstdc++
13), where gl/vao.cpp could not compare vector iterators.

Also drops a stale editor/editorSettings.hpp from the MSVC source list,
which broke the Windows configure step, silences the deliberate
include-in-purview warning in the glm wrapper, and removes GCC support:
clang or MSVC only.

utilities/glm_module.cppm

@@ -40,6 +40,12 @@ export module eu07.glm;
 // merge when the same glm declarations arrive from several different modules
 // ("conflicting imported declaration" on glm::detail::storage), so glm has to be
 // compiled into exactly one module.
+// Clang warns that including inside the purview attaches the declarations to
+// this module. That is exactly the point here, so silence it for this block.
+#ifdef __clang__
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Winclude-angled-in-module-purview"
+#endif
 export {
 #include <glm/glm.hpp>
 #include <glm/fwd.hpp>
@@ -62,6 +68,9 @@ export {
 // call sites of glm::to_string include it in their own module fragment.
 #include <glm/gtx/transform.hpp>
 }
+#ifdef __clang__
+#pragma clang diagnostic pop
+#endif
 
 export {
 // 12-byte vec3 that stays packed regardless of GLM_FORCE_DEFAULT_ALIGNED_GENTYPES.