Look for map files in a "Maps" subfolder, with root fallback

[THandke]

Summary

• Player currently only looks for MapNNNN.lmu/.emu files directly in the game's root folder. This adds support for storing them in a Maps subfolder instead, for a tidier project layout.
• Lookup prefers Maps/ but falls back to the root directory when a map isn't found there, so the large existing library of RPG Maker 2000/2003 games (which universally keep maps in the root) keeps working unmodified.
• Touches map loading (Game_Map::LoadMapFile), async map prefetching (Game_Map::RequestMap, relevant for Emscripten), the start-map existence check that triggers non-standard-extension guessing (DefaultLmuStartFileExists), and the non-standard LMU extension guesser (FileExtGuesser::GuessAndAddLmuExtension).

Why no RPG_RT.lmt (TreeMap) changes

RPG_RT.lmt only stores map IDs, names, hierarchy and per-map metadata — never file paths. The ID-to-filename mapping (MapNNNN.lmu) is a pure Player-side convention, so lcf::LMT_Reader parsing needed no changes; only the file-lookup logic that turns a map ID into an on-disk path was updated.

Reviewer notes

• New shared helper Game_Map::FindMapFile() centralizes the "try Maps/, then fall back to root" logic so LoadMapFile, RequestMap, and DefaultLmuStartFileExists stay consistent.
• Probing a nonexistent Maps/ directory is cheap and silent: DirectoryTree::FindFile caches missing-directory lookups and defaults file_not_found_warning to false (existing pattern used elsewhere in this codebase for the same reason).
• I was not able to compile or run the test suite in the environment this was authored in (no C++ toolchain available). Changes were verified by careful manual/static review of signatures, includes, and call sites, but a local build + ctest before merging is strongly recommended.

🤖 Generated with Claude Code

[carstene1ns]

jenkins: ok to test

[Ghabry]

Hi.

You didn't set an author for your git commit. It is just "Your Name".

For consistency with other folders it should be called "Map" instead of "Maps".

The logic in RequestMap for the web player will not work this way: When the map was not requested it is not available in the file system yet so the condition will be always false. Instead this needs additional logic in the AsyncHandler class to fetch the correct file depending on its existance.