feat(client): opt-in "Rumble on this phone" mirrors pad-0 rumble onto the device

iOS + Android: a new opt-in setting mirrors controller 1's rumble onto the
device's own actuator (Apple RumbleRenderer Actuator.device / CoreHaptics,
Android deviceBodyVibrator), so a motor-less clip-on pad still gives haptic
feedback through the phone/tablet it's clamped to. Default off; wired through
the gamepad settings on both platforms.

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

clients/apple/Sources/PunktfunkClient/Settings/GamepadSettingsView.swift

@@ -15,6 +15,9 @@ import PunktfunkKit
 import SwiftUI
 #if os(iOS) || os(macOS) || os(tvOS)
 import GameController
+#if os(iOS)
+import CoreHaptics
+#endif
 
 struct GamepadSettingsView: View {
     @Environment(\.dismiss) private var dismiss
@@ -38,6 +41,9 @@ struct GamepadSettingsView: View {
     @AppStorage(DefaultsKey.gamepadUIEnabled) private var gamepadUIEnabled = true
     @AppStorage(DefaultsKey.autoWake) private var autoWakeEnabled = true
     @AppStorage(DefaultsKey.presenter) private var presenter = SettingsOptions.presenterDefault
+    #if os(iOS)
+    @AppStorage(DefaultsKey.rumbleOnDevice) private var rumbleOnDevice = false
+    #endif
     @ObservedObject private var gamepads = GamepadManager.shared
 
     #if os(iOS)
@@ -230,7 +236,7 @@ struct GamepadSettingsView: View {
             .map { (label: "\($0) Hz", tag: $0) }
         let bitrate = SettingsOptions.bitrateOptions(current: bitrateKbps)
         let controllers = SettingsOptions.controllerOptions(gamepads)
-        return [
+        var list: [Row] = [
             choiceRow(
                 id: "resolution", header: "Stream", icon: "aspectratio",
                 label: "Resolution",
@@ -329,6 +335,23 @@ struct GamepadSettingsView: View {
                 detail: "Turn off to use the touch interface even with a controller connected.",
                 value: $gamepadUIEnabled),
         ]
+        #if os(iOS)
+        // The device-rumble mirror slots in after "Controller type" (staying inside the
+        // Controller group — the next row carries the "Interface" header). iPhone only in
+        // practice: hidden where the device itself can't play haptics (iPad).
+        if CHHapticEngine.capabilitiesForHardware().supportsHaptics,
+            let at = list.firstIndex(where: { $0.id == "padType" }) {
+            list.insert(
+                toggleRow(
+                    id: "deviceRumble", icon: "iphone.radiowaves.left.and.right",
+                    label: "Rumble on this iPhone",
+                    detail: "Also play player 1's rumble on the phone's own Taptic Engine — "
+                        + "for clip-on pads without rumble motors.",
+                    value: $rumbleOnDevice),
+                at: at + 1)
+        }
+        #endif
+        return list
     }
 
     /// Resolution choices as "WxH" tags — the current size is inserted when it's a custom mode

clients/apple/Sources/PunktfunkClient/Settings/SettingsView+Sections.swift

@@ -1,6 +1,9 @@
 // SettingsView's shared sections — each setting's Section is defined exactly once here and
 // composed by the per-platform bodies in SettingsView.swift.
 
+#if os(iOS)
+import CoreHaptics
+#endif
 import PunktfunkKit
 import SwiftUI
 
@@ -471,6 +474,12 @@ extension SettingsView {
                     Text(option.label).tag(option.tag)
                 }
             }
+            #if os(iOS)
+            // iPhone only in practice: hidden where the device itself can't play haptics (iPad).
+            if CHHapticEngine.capabilitiesForHardware().supportsHaptics {
+                Toggle("Rumble on this iPhone", isOn: $rumbleOnDevice)
+            }
+            #endif
             #if !os(tvOS)
             Toggle("Gamepad-optimized browsing", isOn: $gamepadUIEnabled)
             #endif
@@ -487,6 +496,11 @@ extension SettingsView {
             // for its own footer and has no such toggle to describe.
             VStack(alignment: .leading, spacing: 6) {
                 Text(Self.controllersFooter)
+                #if os(iOS)
+                if CHHapticEngine.capabilitiesForHardware().supportsHaptics {
+                    Text(Self.deviceRumbleFooter)
+                }
+                #endif
                 #if !os(tvOS)
                 Text(Self.gamepadUIFooter)
                 #endif

clients/apple/Sources/PunktfunkClient/Settings/SettingsView+Support.swift

@@ -88,6 +88,13 @@ extension SettingsView {
         + "controller (a DualSense keeps adaptive triggers, lightbar, touchpad and motion). "
         + "Applies from the next session."
 
+    #if os(iOS)
+    static let deviceRumbleFooter =
+        "Rumble on this iPhone plays player 1's rumble on the phone's own Taptic Engine as "
+        + "well — for clip-on controllers that have no rumble motors of their own. Applies "
+        + "from the next session."
+    #endif
+
     #if !os(tvOS)
     static let gamepadUIFooter =
         "When a controller connects, the host list and library switch to a controller-"

clients/apple/Sources/PunktfunkClient/Settings/SettingsView.swift

@@ -55,6 +55,7 @@ struct SettingsView: View {
     #if os(iOS)
     @AppStorage(DefaultsKey.pointerCapture) var pointerCapture = true
     @AppStorage(DefaultsKey.touchMode) var touchMode = TouchInputMode.trackpad.rawValue
+    @AppStorage(DefaultsKey.rumbleOnDevice) var rumbleOnDevice = false
     // The sidebar selection drives the detail pane on iPad and the pushed sub-page on iPhone.
     // Width class decides the initial value: nil on iPhone (show the category list first),
     // General on iPad (a two-column layout should never open with an empty detail).