feat(gamepad): pure-user-mode Windows DualShock 4 + Xbox 360 (drop ViGEm) + installer + multi-pad

Windows virtual gamepads now have zero external dependencies - ViGEmBus is removed.

- DualShock 4: Windows UMDF backend (inject/dualshock4_windows.rs + dualshock4_proto.rs),
  reusing the DualSense SwDeviceCreate game-detection identity fix. The one UMDF driver serves
  the DS5 or DS4 identity/descriptor/features/strings per a device_type byte the host stamps into
  shared memory. Driver also gains IOCTL_HID_GET_STRING and a 41-byte calibration feature.
- Xbox 360: a new UMDF2 XUSB companion driver (packaging/windows/xusb-driver/) that registers
  GUID_DEVINTERFACE_XUSB and answers the buffered XInput IOCTLs from a shared section, so classic
  XInputGetState/SetState work with no kernel bus driver. inject/gamepad_windows.rs is rewritten
  to drive it and the vigem-client dependency is removed. Xbox One folds to the 360 XInput path.
- Installer: vendor + pnputil-install the three UMDF drivers (packaging/windows/gamepad-drivers/
  + install-gamepad-drivers.ps1, wired into pack-host-installer.ps1 + punktfunk-host.iss).
- Multi-pad: the host stamps each pad index into the device Location (pszDeviceLocation); the
  driver reads it via WdfDeviceAllocAndQueryProperty to map its own *-shm-<index>, with
  UmdfHostProcessSharing=ProcessSharingDisabled giving each pad its own host (per-pad statics).

Validated live on the Windows host: Cyberpunk native DualSense detection, DS4 identity + descriptor,
XInputGetState + rumble round-trip, two pads -> two distinct XInput slots, and a full installer build.

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

crates/punktfunk-host/src/inject.rs

@@ -432,13 +432,20 @@ pub mod dualsense_proto;
 pub mod dualsense_windows;
 #[cfg(target_os = "linux")]
 pub mod dualshock4;
+/// Transport-independent DualShock 4 HID codec used by the Windows UMDF-driver backend
+/// ([`dualshock4_windows`]). (The Linux backend still carries its own copy — see the module FIXME.)
+#[cfg(any(target_os = "linux", target_os = "windows"))]
+pub mod dualshock4_proto;
+/// Windows: virtual DualShock 4 via the same UMDF minidriver + shared-memory channel (device-type 1).
+#[cfg(target_os = "windows")]
+pub mod dualshock4_windows;
 #[cfg(target_os = "linux")]
 pub mod gamepad;
-/// Windows: virtual Xbox 360 pads via ViGEmBus.
+/// Windows: virtual Xbox 360 pads via the in-tree XUSB companion UMDF driver (classic XInput).
 #[cfg(target_os = "windows")]
 #[path = "inject/gamepad_windows.rs"]
 pub mod gamepad;
-/// Stub — virtual gamepads need Linux uinput or Windows ViGEmBus; events are dropped elsewhere.
+/// Stub — virtual gamepads need Linux uinput or the Windows UMDF drivers; events are dropped elsewhere.
 #[cfg(not(any(target_os = "linux", target_os = "windows")))]
 pub mod gamepad {
     #[derive(Default)]