feat: add rocker toggle style

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

Sources/SstUI/Controls.swift

@@ -105,3 +105,39 @@ public struct LampView: View {
             .accessibilityHidden(true)
     }
 }
+
+/// A two-position rocker switch: a key cap sliding in a recessed track.
+public struct RockerToggleStyle: ToggleStyle {
+    public init() {}
+
+    public func makeBody(configuration: Configuration) -> some View {
+        HStack(spacing: Space.s4) {
+            configuration.label
+            Button {
+                configuration.isOn.toggle()
+            } label: {
+                RockerTrack(isOn: configuration.isOn)
+            }
+            .buttonStyle(.plain)
+            .accessibilityValue(configuration.isOn ? "aan" : "uit")
+        }
+    }
+
+    private struct RockerTrack: View {
+        let isOn: Bool
+        @Environment(\.accessibilityReduceMotion) private var reduceMotion
+
+        var body: some View {
+            ZStack(alignment: isOn ? .trailing : .leading) {
+                WellBackground()
+                PhysicalSurface(
+                    fill: AnyShapeStyle(LinearGradient(colors: [Palette.surfaceKeyHigh, Palette.surfaceKeyLow], startPoint: .top, endPoint: .bottom)),
+                    cornerRadius: Radius.sm, shadows: Shadows.keyRaised)
+                    .frame(width: Size.switchWidth / 2, height: Size.switchHeight - Space.s2)
+                    .padding(Space.s1)
+            }
+            .frame(width: Size.switchWidth, height: Size.switchHeight)
+            .animation(reduceMotion ? nil : .easeOut(duration: Motion.durationFast), value: isOn)
+        }
+    }
+}