feat(apple): multi-controller support

Roll the pf-client-core slot pattern to the Apple client (Swift):

- GamepadManager tracks all connected GCControllers, assigning each a stable
  lowest-free wire pad index + concrete type, emitting GamepadArrival on
  connect and GamepadRemove on disconnect (index freed for reuse on re-plug).
- GamepadCapture binds every controller with per-controller Slot state
  (buttons/axes/fingers/motion), threading the pad index into flags on every
  event; GamepadWire/InputEvents carry the pad + the two new events.
- GamepadFeedback + RumbleRenderer go per-pad (rumbleByPad, slots[pad]),
  routing rumble/HID back to the correct controller by wire index.
- ContentView/Settings surface every forwarded controller.

pad 0 => flags 0, so single-controller wire is byte-identical. Cannot build
on the Linux dev box (no Swift toolchain / Apple frameworks); wire bytes
hand-checked against input.rs and GamepadWireTests extended for multi-pad.
CI apple.yml (swift build/test on macOS) is the compile gate.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

clients/apple/Sources/PunktfunkClient/Session/SessionModel.swift

@@ -419,9 +419,10 @@ final class SessionModel: ObservableObject {
             micChannel: defaults.integer(forKey: DefaultsKey.micChannel),
             micEnabled: defaults.object(forKey: DefaultsKey.micEnabled) as? Bool ?? true)
         self.audio = audio
-        // Gamepads: forward GamepadManager's active controller as pad 0 and render the
-        // host's feedback (rumble always; lightbar/player-LEDs/adaptive-triggers when the
-        // session's virtual pad is a DualSense). Same trust gate as audio — nothing is
+        // Gamepads: forward every controller GamepadManager selected — each on its own wire pad
+        // index (a pin forwards only one, Automatic forwards all) — and render the host's feedback
+        // back to the pad it's addressed to (rumble always; lightbar/player-LEDs/adaptive-triggers
+        // when a pad's virtual device is a DualSense). Same trust gate as audio — nothing is
         // forwarded during the trust prompt.
         let capture = GamepadCapture(connection: conn, manager: .shared)
         // The cross-client escape chord (hold L1+R1+Start+Select 1.5 s) — on tvOS the only