Native game-loop playback

The player runs the recovered SPC snapshot continuously in a worker with Game
Music Emu, compiled to WebAssembly. The original SNES driver executes the song's
own intro and repeating sequence; it does not restart or loop a faded MP3.

Duration and fade hints are zeroed only in the worker's in-memory playback copy.
The original downloaded SPC snapshot is unchanged. No fade is scheduled. This
mode is offered for the eighteen music cues whose original driver loops.

NinjaSpcPlayer and its worker are original project integration code. The vendor
Web-GME-Player.js and Web-GME-Player.wasm are from Thysbelon's Web-GME-Player,
revision 0f2f8b6290bb9aac6a6168875afbf252dcd183b4. Its README explicitly provides
the files for embedding music in websites. The original bridge source and build
instructions are retained in vendor/main.c and vendor/README.md.

Game Music Emu is LGPL software. Its notices, exact upstream source archive
(935295234086482e6d36be5db787cfee4f0b4aea, identified by the bridge README), and
build instructions are supplied in vendor/. The WASM and loader stay separate
files and can be replaced with a compatible rebuilt module. See vendor/license.txt,
vendor/license.gpl2.txt, vendor/game-music-emu-source.zip and vendor/provenance.json.