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/punktfunk-host.iss

@@ -32,6 +32,10 @@
 #ifdef StageDir
   #define WithDriver
 #endif
+; GamepadStageDir (the vendored UMDF gamepad drivers + install-gamepad-drivers.ps1) is optional.
+#ifdef GamepadStageDir
+  #define WithGamepad
+#endif
 ; FfmpegBin (a dir of FFmpeg shared DLLs) is optional — present when the host is built with
 ; --features amf-qsv (the AMD/Intel AMF/QSV encode backend link-imports the FFmpeg libs).
 #ifdef FfmpegBin
@@ -67,6 +71,9 @@ Name: "english"; MessagesFile: "compiler:Default.isl"
 #ifdef WithDriver
 Name: "installdriver"; Description: "Install the SudoVDA virtual display driver (required for native-resolution streaming)"
 #endif
+#ifdef WithGamepad
+Name: "installgamepad"; Description: "Install the virtual gamepad drivers (DualSense / DualShock 4 / Xbox 360 — no ViGEmBus needed)"
+#endif
 Name: "startservice"; Description: "Start the punktfunk host service now (also starts on every boot)"
 
 [Files]
@@ -83,6 +90,10 @@ Source: "{#FfmpegBin}\*.dll"; DestDir: "{app}"; Flags: ignoreversion
 ; The driver payload + nefconc.exe + install-sudovda.ps1, extracted to {tmp} and removed after install.
 Source: "{#StageDir}\*"; DestDir: "{tmp}\sudovda"; Flags: deleteafterinstall recursesubdirs createallsubdirs; Tasks: installdriver
 #endif
+#ifdef WithGamepad
+; The vendored UMDF gamepad drivers + install-gamepad-drivers.ps1, extracted to {tmp}, removed after.
+Source: "{#GamepadStageDir}\*"; DestDir: "{tmp}\gamepad"; Flags: deleteafterinstall recursesubdirs createallsubdirs; Tasks: installgamepad
+#endif
 
 [Run]
 #ifdef WithDriver
@@ -91,6 +102,12 @@ Filename: "powershell.exe"; \
   StatusMsg: "Installing the SudoVDA virtual display driver..."; \
   Flags: runhidden waituntilterminated; Tasks: installdriver
 #endif
+#ifdef WithGamepad
+Filename: "powershell.exe"; \
+  Parameters: "-NoProfile -ExecutionPolicy Bypass -File ""{tmp}\gamepad\install-gamepad-drivers.ps1"" -Dir ""{tmp}\gamepad"""; \
+  StatusMsg: "Installing the virtual gamepad drivers..."; \
+  Flags: runhidden waituntilterminated; Tasks: installgamepad
+#endif
 ; Register (or re-point, on upgrade - idempotent) the SYSTEM service from its FINAL {app} location:
 ; service install records current_exe() as the SCM binPath, so it must run from {app}, not {tmp}.
 Filename: "{app}\punktfunk-host.exe"; Parameters: "service install"; WorkingDir: "{app}"; \