Add game library with folder scanning and filtered list UI

[Copilot]

Implements a game library that scans configured folders for ROMs and displays them in a searchable, sortable list in the Load Game overlay.

Implementation

Data structures:

• se_game_library_entry_t - stores path, name, and system type (GB/GBC/GBA/NDS)
• se_game_library_state_t - tracks 2048 entries max with sorted indices
• Extended se_search_paths_t using existing padding slots for 3 library paths
• Added game_library_recursive_scan flag to persistent_settings_t

Scanning:

• Uses tinydir for directory traversal with optional recursion
• Detects system type by file extension (.gb, .gbc, .gba, .nds)
• ZIP files excluded (require extraction for type detection)
• Auto-rescans on path changes, manual trigger available

UI additions:

• Settings panel: 3 configurable paths, recursive scan toggle, manual rescan
• Load Game overlay: filtered/sorted game list with system badges
• Reuses existing search buffer and UI components
• Alphabetical sort (asc/desc)

Code quality:

• Bounds checking in comparators
• Buffer sizes use sizeof() and named constants
• Sort validation in sort function, not per-frame
• ~240 LOC in src/main.c only, no ABI changes

Original prompt

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This section details on the original issue you should resolve

<issue_title>Feature Request: Game List</issue_title>
<issue_description>Would it be possible to implement a game list where you can add folder(s) that the program scans for games and automatically adds them to a list shown when the emulator is launched? I feel like one that's similar to Dolphin's would work well with the overall style of the program. Some extras like recursive folder searching, being able to exit back to the game list and (maybe?) a cover downloading framework would go well with it, but those are just suggestions.</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Feature Request: Game List #519

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[github-actions]

Web build for 9e0074e will be live at https://web.skyemu.app/commit/9e0074edd48f216b4026d0ef3324a2c9d8cdb947/index.html