Add Animal Crossing texture factories

[mckinlee]

Summary

• add bounded directory-source reads and exact Animal Crossing (USA revision 0) game-file ownership
• add shared GameCube texture/Yaz0 support for the initial boy1 BTI, all 255 player cloths, 15 cat texture sets, and 49 item billboards
• add renderer-neutral texture thumbnails plus source-free validators distributed across existing Release matrix jobs

Testing

• clean MSVC x64 Release builds with BUILD_UI=ON and BUILD_UI=OFF
• all five source-free validators against both Release executables
• BUILD_AC=OFF compile-out build
• existing-work-directory refusal checks
• clang-format dry run, Python syntax, workflow YAML, diff, path, and leakage checks
• DirectX synthetic boy1 open/select/thumbnail/close journey on a temporary stack with Package viewer shaders and harden LUS startup #245

The conversion and validator paths are independent of #244 and #245. The stacked viewer journey uses #245 only for its pending packaged-viewer startup fix.