feat(host/windows): DXGI Desktop Duplication capture backend

Windows Capturer via DXGI Desktop Duplication: create a D3D11 device on the SudoVDA adapter (by LUID), find the matching output (by GDI name), DuplicateOutput, and per AcquireNextFrame copy the desktop into a CPU-readable staging texture -> tightly-packed BGRA (FramePayload::Cpu, feeds the openh264 software encoder GPU-lessly). Handles WAIT_TIMEOUT (reuse last frame) and ACCESS_LOST (re-duplicate). Adds FramePayload::D3d11(D3d11Frame) for the future NVENC zero-copy path, and a VirtualOutput.win_capture identity (adapter LUID + GDI name) carried out of the SudoVDA backend. Pure helpers (pack_luid/gdi_name_matches/depad_bgra) unit-tested on the VM; the live duplication path needs a real GPU + an activated SudoVDA monitor. Compiles clean on Windows + Linux.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/punktfunk-host/Cargo.toml

@@ -116,6 +116,11 @@ windows = { version = "0.62", features = [
     "Win32_UI_Input_KeyboardAndMouse",
     "Win32_UI_WindowsAndMessaging",
     "Win32_System_StationsAndDesktops",
+    "Win32_Graphics_Dxgi",
+    "Win32_Graphics_Dxgi_Common",
+    "Win32_Graphics_Direct3D",
+    "Win32_Graphics_Direct3D11",
+    "Win32_Graphics_Gdi",
 ] }
 # Software H.264 encoder (GPU-less path + NVENC fallback). The default `source` feature statically
 # compiles OpenH264 (BSD-2) — no system lib, builds on MSVC; nasm on PATH adds the SIMD fast path.