feat(apple/gamepad): claim controller system gestures during capture — PS button opens the Steam overlay, share/create stops screenshotting locally

While a pad drives a stream, GamepadCapture now sets EVERY element's
preferredSystemGestureState to .disabled (restored to .enabled on unbind).
iOS/macOS attach system gestures to several controller buttons — share/create
took a LOCAL screenshot instead of reaching the game, and only the Home
element was opted out before. With the gestures claimed, the already-wired
chains do their job: PS/Home → wire guide → BTN_MODE on the virtual xpad
(the Steam-overlay button) / the PS bit on the virtual DualSense.

Also fold the share/create/capture element (GCInputButtonShare) into the
back/select wire bit — clone pads like the GameSir G8 expose their screenshot
button only as the share element, not buttonOptions (OR onto the same bit, so
double-exposed pads are harmless). The G8's other extra button (M) is a
firmware-local modifier (turbo/hair-trigger/swap) invisible to the OS.

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

CLAUDE.md

@@ -168,7 +168,10 @@ Low-latency desktop/game streaming stack, Linux-first, with a shared Rust protoc
    controller discovery + selection in Settings (`GamepadManager` — exactly one pad
    forwarded as pad 0, auto or pinned; pad TYPE auto-resolves from the physical
    controller, user-overridable), capture incl. DualSense touchpad/motion
-   (`GamepadCapture`/`GamepadWire`), feedback rendering (rumble → CoreHaptics; lightbar /
+   (`GamepadCapture`/`GamepadWire`; while streaming, EVERY element's
+   `preferredSystemGestureState` is claimed `.disabled` — share/create reaches the host as
+   select instead of screenshotting locally, PS/Home reaches the host as guide/`BTN_MODE` =
+   the Steam-overlay button — restored `.enabled` on unbind), feedback rendering (rumble → CoreHaptics; lightbar /
    player LEDs / adaptive triggers → `GCDeviceLight`/`playerIndex`/
    `GCDualSenseAdaptiveTrigger` via the table-driven `DualSenseTriggerEffect` parser).
    Loopback-tested end to end (`PUNKTFUNK_TEST_FEEDBACK=1` scripted burst); DualSense