chore(host/windows): clean up DDA capture — fix unused imports, quiet secure-desktop log, sane retry default

- Remove 4 unused imports (PCWSTR in composed_flip, anyhow macro + SizeInt32 in
  wgc, Write in wgc_relay).
- DuplicateOutput1 retry defaults to N=1 (immediate legacy): on the secure
  desktop DuplicateOutput1 is LOGON_UI-only so it always refuses, and the
  release-before-reduplicate + gentle recovery keep the legacy dup stable;
  retrying there only blocked. Still env-tunable (PUNKTFUNK_DUP_RETRY_N/_MS).
- Throttle the 'using legacy DuplicateOutput' warning (expected + once-per-gentle-
  recovery on secure) so a lock dwell doesn't flood the log.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

crates/punktfunk-host/src/capture/wgc.rs

@@ -20,7 +20,7 @@ use super::dxgi::{
     find_output, make_device, nudge_cursor_onto, D3d11Frame, HdrConverter, WinCaptureTarget,
 };
 use super::{CapturedFrame, Capturer, FramePayload, PixelFormat};
-use anyhow::{anyhow, bail, Context, Result};
+use anyhow::{bail, Context, Result};
 use std::sync::atomic::{AtomicU64, Ordering};
 use std::sync::{Arc, Condvar, Mutex};
 use std::time::{Duration, Instant};
@@ -30,7 +30,6 @@ use windows::Graphics::Capture::{
     Direct3D11CaptureFrame, Direct3D11CaptureFramePool, GraphicsCaptureItem, GraphicsCaptureSession,
 };
 use windows::Graphics::DirectX::DirectXPixelFormat;
-use windows::Graphics::SizeInt32;
 use windows::Win32::Foundation::{CloseHandle, HANDLE};
 use windows::Win32::Graphics::Direct3D11::{
     ID3D11Device, ID3D11DeviceContext, ID3D11RenderTargetView, ID3D11ShaderResourceView,