Add src/installer-rp/ytdlp.ts that downloads
https://github.com/yt-dlp/yt-dlp/releases/latest/download/yt-dlp.exe
into %appdata%/.mc_custom/yt-dlp.exe (fixed path, Windows-only since
the installer is shipped as .exe). If the file is already there and
--version works it is reused; otherwise it is re-downloaded and
verified. The server's existing OS-aware ensureYtDlp stays intact.
The install IPC handler now calls ensureYtDlpExe() in step 2-1 and
logs the resolved path. Music / image / zip / place steps are still
stubbed.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
