v0.1.0: Metal Slug on recompiled code, with sound and gamepads

Added

• Gamepads: the toolkit is pinned at neogeorecomp v0.2.0 (af96b2b), which reads up to two SDL2 gamepads as players 1 and 2 (neogeorecomp #6).
• Sound: the toolkit is pinned at neogeorecomp #3 (YM2610 synthesis through ymfm). The window plays it, --wav FILE writes it, --mute silences it. The build now enables C++ for ymfm, and setup.sh checks for g++. Sound is by @danilopaulinodasilva (neogeorecomp #3).
• CI: builds the interpreter-only player on Ubuntu, Windows and macOS on every push and PR.
• Installer (recomp-launcher): launcher/launcher.json and the installer workflow build Metal-Slug-Installer for Windows, Linux and macOS on every push; a v* tag attaches them to the release.
• setup.sh runs on macOS (Homebrew), and both setup scripts print [n/N] steps for the installer's progress bar. On Windows, installing Git or CMake no longer stops setup for a rerun.
• Boots and plays on the rebuilt neogeorecomp: the real MVS BIOS, attract mode, coin/start, and Mission 1, running on recompiled 68000 code (needs neogeorecomp #1).
• mslug_recomp, the generator that recompiles the user's own ROMs into build/generated at build time (MSLUG_ROM_DIR).
• The profile target: headless attract and play sessions record runtime-only entry points; the next build includes them.
• tests/coin_start.txt (reach Mission 1) and tests/play_long.txt (5-minute soak).
• Setup.cmd / setup.sh quick start: prerequisite checks that ask before installing, ROM discovery with CRC checks, build, profile, launcher.
• neogeorecomp as a git submodule; toolkit.ref pins it for plain downloads.
• README with Getting Started and screenshots; docs/game-notes.md.

Removed

• The scaffold's placeholder notes and empty recomp/ directory.

Installers (Windows, Linux, macOS) are attached below once the installer workflow finishes. They hold no game data: pick the folder with your own MAME zips and they build the game on your machine. Built on neogeorecomp v0.2.0.