Fixed three macOS bugs (save-state crash, blank Input settings, ROM double-click)

[mysterypaintwo]

This PR fixes three unrelated bugs, all reproduced and verified on Apple Silicon (macOS 26 Tahoe). None of the changes affect SNES emulation (sfc/, processor/); they are limited to save-state I/O, UI, and macOS integration.

1. Fix save-state load crash (heap corruption).
   nall::Decode::RLE reconstructed the uncompressed size using undefined behavior (shifting a promoted 32-bit value by up to 56 bits), producing an invalid allocation size on arm64. This corrupted the heap during decompression and caused a crash shortly afterward. The decoder now matches the encoder's 64-bit implementation.

2. Fix empty Input/Hotkeys mapping list on first open.
   SettingsWindow::show() activated the window through the base Window class, bypassing SettingsWindow::setVisible(), which refreshes the mapping list. As a result, mappings only appeared after changing the device dropdown. The mappings are now refreshed whenever the window is shown.

3. Fix opening ROMs via Finder ("Open With" / double-click).
   bsnes previously had no document-opening path on macOS because Info.plist did not declare supported document types and no Apple Event handler was registered. This PR:

   • registers a kAEOpenDocuments handler early in startup,
   • buffers open requests until the application is ready, and
   • adds document type declarations for supported ROM formats (.sfc, .smc, .gb, .gbc, .bs, .st) using LSHandlerRank: Alternate.

   During testing I also found duplicate LaunchServices registrations can prevent file opening on some development systems. That's an environment issue rather than a code bug, but reviewers who can't reproduce may want to clear stale registrations with lsregister.

Testing

Verified manually on Apple Silicon (macOS 26 Tahoe):

• Save-state load no longer crashes.
• Settings -> Input/Hotkeys populates mappings immediately on first open.
• Opening a ROM via Finder (open -a bsnes.app romfile.sfc) with no bsnes process running beforehand (confirmed via ps) successfully launches the emulator and loads the ROM. This distinction matters: an already-running instance receives document-open events through a different path and would pass even without this fix, so this was specifically tested as a cold launch.
• Loaded the alttpo AngelScript script folder with no errors, confirming AngelScript's arm64 support (already present on this branch's unstable base) works correctly alongside these fixes.