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>

packaging/windows/xusb-driver/pf_xusb.inx

@@ -0,0 +1,64 @@
+;/*++
+; punktfunk virtual Xbox 360 XUSB companion — a non-HID UMDF2 driver that registers the XUSB
+; device-interface GUID {EC87F1E3-...} and answers the buffered XInput IOCTLs, so classic
+; XInputGetState() reads the pad without a kernel bus driver (the HIDMaestro approach). System class,
+; hosted by the in-box WUDFRd reflector. Created per-session by the host via SwDeviceCreate
+; (hardware id `pf_xusb`); `root\pf_xusb` is the devgen/devcon test id.
+;--*/
+[Version]
+Signature   = "$WINDOWS NT$"
+Class       = System
+ClassGuid   = {4D36E97D-E325-11CE-BFC1-08002BE10318}
+Provider    = %ProviderString%
+CatalogFile = pf_xusb.cat
+PnpLockdown = 1
+
+[DestinationDirs]
+DefaultDestDir = 13
+
+[SourceDisksNames]
+1 = %DiskId1%,,,""
+
+[SourceDisksFiles]
+pf_xusb.dll = 1,,
+
+[Manufacturer]
+%StdMfg%=Standard, NT$ARCH$.10.0...22000
+
+[Standard.NT$ARCH$.10.0...22000]
+%DeviceDesc%=pfXusb, root\pf_xusb, pf_xusb
+
+[pfXusb.NT]
+CopyFiles=Drivers_Dir
+Include=WUDFRD.inf
+Needs=WUDFRD.NT
+
+[Drivers_Dir]
+pf_xusb.dll
+
+[pfXusb.NT.HW]
+Include=WUDFRD.inf
+Needs=WUDFRD.NT.HW
+
+[pfXusb.NT.Services]
+Include=WUDFRD.inf
+Needs=WUDFRD.NT.Services
+
+[pfXusb.NT.Wdf]
+UmdfService=pf_xusb, pfXusb_Install
+UmdfServiceOrder=pf_xusb
+UmdfKernelModeClientPolicy=AllowKernelModeClients
+UmdfFileObjectPolicy=AllowNullAndUnknownFileObjects
+UmdfMethodNeitherAction=Copy
+UmdfFsContextUsePolicy=CanUseFsContext2
+UmdfHostProcessSharing=ProcessSharingDisabled
+
+[pfXusb_Install]
+UmdfLibraryVersion=$UMDFVERSION$
+ServiceBinary=%13%\pf_xusb.dll
+
+[Strings]
+ProviderString = "punktfunk"
+StdMfg         = "(Standard system devices)"
+DiskId1        = "punktfunk XUSB Installation Disk"
+DeviceDesc     = "punktfunk Virtual Xbox 360 (XUSB)"