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`m3-host wgc-helper --target-id N --gdi NAME --mode WxHxHz --bitrate K`: the USER-session half of the two-process secure-desktop design (docs/windows-secure-desktop.md). Opens WGC on the EXISTING SudoVDA output by GDI name only (never creates a virtual output — a second topology owner re-trips the ACCESS_LOST born-lost storm), encodes via NVENC, and ships framed Annex-B AUs on stdout for the SYSTEM host to relay onto the live QUIC session: `[u32 magic "PFAU"][u32 len][u64 pts_ns][u8 keyframe][data]`. tracing → stderr so stdout stays the pure AU stream. cfg-gated windows-only; Linux build unaffected. scripts/headless/win-build.cmd: the canonical box build script (sets PUNKTFUNK_BUILD_VERSION so build.rs stamps the version + the NVENC LIB path). Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>