Misc Fixes for 2026/09/26

[Areloch]

• Fix the check for the World Editor guis in the CMakeLists so that it doesn't erroneously shove it into a /source subfolder in the solution
• Add a check during asset import that if the config normally always forces a material suffix, we do a check without the suffix to see if we have a match too, so we don't erroneously duplicate a material that actually already exists
• Fix the item testbox's max extent
• Make the mBackground in the guiPopUp classes be a SimObjectPtr to manage the object ref a little more sanely
• In the event another canvas is made, added sanity check to avoid erroneously re-processing the SFX system, which could cause a crash
• Fixed TypeMatrixF to properly set and get the full matrix value
• Added helper functions to fully copy the aiNodeAnim and aiMeshAnim classes as they don't have copy constructors, so when processing data in AssimpAppSequence, the copying of the data could leave room for incomplete/shallow copies, or hanging memory. The util functions do a full clone copy, so there's no hanger-ons with the memory, and is safe to clean up at any time
• Associated to above, but also expressly added cleanup to that data
• in TSShape's initMaterialList and buildConvexHull, added + start so the end range is properly offset