feat(windows): IddCx hardware-cursor channel — remote-desktop sweep M2c

Brings the cursor channel to Windows hosts. The pf-vdisplay driver
declares an IddCx hardware cursor for sessions that negotiated
cursor-forward — DWM then EXCLUDES the pointer from the IDD frame and
delivers shape/position out-of-band, into the same CursorOverlay →
forwarder → wire → client pipeline the Linux portal path uses.

- pf-driver-proto v5 (additive, host floor stays 3): AddRequest's spare
  tail becomes hw_cursor (same size/offsets); IOCTL_SET_CURSOR_CHANNEL
  delivers a host-created CursorShm section (64-byte seqlock header +
  256² shape buffer, layout pinned + tested). No event crosses the
  boundary — the host polls at encode-tick pace.
- driver: wdk-iddcx grows the two cursor DDI wrappers; a per-monitor
  cursor worker (event wait → QueryHardwareCursor → seqlock publish)
  starts only when BOTH the ADD asked and the channel arrived, so a
  failed delivery leaves DWM compositing as today. Shape bytes ship raw
  (BGRA/masked + pitch); the host converts.
- host: the section rides the existing sealed-channel broker (least-
  privilege dup, remote reap on failure); IddPushCapturer::cursor()
  seqlock-reads → CursorOverlay (BGRA→RGBA, masked-color approximation,
  desktop→frame origin shift, per-shape conversion cache). New
  Capturer::cursor() trait hook — the encode loop prefers it over the
  frame-attached overlay because hardware-cursor moves produce NO new
  frame on a static desktop. hw_cursor survives the re-arrival resize
  (carried on the manager's Monitor).
- negotiation: cursor_forward grows the Windows arm (client cap ∧
  driver proto ≥ 5, probed once via the control device); SessionPlan
  carries cursor_forward → OutputFormat.hw_cursor.
- drive-by: wdk-probe's two pre-existing same-type casts (clippy) and
  pf-vdisplay's stale spike-test refs (crate::win_display moved to
  pf-win-display; tracing-subscriber was never a dep) repaired.

Verified: proto tests on Mac AND MSVC (15/15 incl. the CursorShm
layout pin); clippy -D warnings for proto/frame/capture/vdisplay/host
on Linux (.21) and native Windows (.173); the DRIVER workspace clippy
-D warnings green against the real WDK 10.0.26100 bindgen (DDI names,
enum variants and IDARG layouts all bind). On-box driver deploy +
on-glass validation follow.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

packaging/windows/drivers/wdk-probe/src/iddcx_surface_assert.rs

@@ -84,5 +84,5 @@ const _: fn() = || {
 /// The FP16/HDR adapter flag + high-color-space target cap the driver MUST set (these gate the whole
 /// `*2` callback requirement). Confirms the ModuleConsts paths the port uses — note these enums have NO
 /// `_`-prefixed module (unlike `_IDDFUNCENUM`/`_IDDSTRUCTENUM`).
-const _: u32 = iddcx::IDDCX_ADAPTER_FLAGS::IDDCX_ADAPTER_FLAGS_CAN_PROCESS_FP16 as u32;
-const _: u32 = iddcx::IDDCX_TARGET_CAPS::IDDCX_TARGET_CAPS_HIGH_COLOR_SPACE as u32;
+const _: u32 = iddcx::IDDCX_ADAPTER_FLAGS::IDDCX_ADAPTER_FLAGS_CAN_PROCESS_FP16;
+const _: u32 = iddcx::IDDCX_TARGET_CAPS::IDDCX_TARGET_CAPS_HIGH_COLOR_SPACE;