feat: redesign UI with gamepad-style input monitor

Split the single-file Swift app into model, store, and view files
and rework the layout. The dongle card shows a status pill with an
adaptive info grid; controllers render as cards in an adaptive grid
that fills wider windows; each card uses a gamepad-style
visualization (D-pad, face buttons, stick pads, triggers) instead of
flat indicator rows. The window is now resizable and content reflows
instead of staying a fixed 420pt column.

Co-Authored-By: qwen3.8-27b@q3_k_xl: redesigned app UI and structure

src/app/GamepadViews.swift

@@ -0,0 +1,137 @@
+import SwiftUI
+
+// Gamepad-style visualization of a controller input snapshot: D-pad and face
+// buttons on top, stick pads and triggers below, mirroring the physical
+// layout of an Xbox controller.
+
+struct DPadView: View {
+    let controller: ControllerInput
+
+    var body: some View {
+        VStack(spacing: 3) {
+            cell(.dPadUp)
+            HStack(spacing: 3) {
+                cell(.dPadLeft)
+                RoundedRectangle(cornerRadius: 5)
+                    .fill(Color.secondary.opacity(0.28))
+                    .frame(width: 30, height: 26)
+                cell(.dPadRight)
+            }
+            cell(.dPadDown)
+        }
+    }
+
+    private func cell(_ button: XboxButton) -> some View {
+        let pressed = controller.isPressed(button)
+        return RoundedRectangle(cornerRadius: 5)
+            .fill(pressed ? Color.green : Color.secondary.opacity(0.18))
+            .frame(width: 30, height: 26)
+            .overlay(
+                Image(systemName: button.dPadSymbol ?? "")
+                    .font(.system(size: 9))
+                    .foregroundStyle(pressed ? .white : .secondary)
+            )
+    }
+}
+
+struct FaceButtonsView: View {
+    let controller: ControllerInput
+
+    var body: some View {
+        VStack(spacing: 4) {
+            faceButton(.y)
+            HStack(spacing: 10) {
+                faceButton(.x)
+                faceButton(.b)
+            }
+            faceButton(.a)
+        }
+    }
+
+    private func faceButton(_ button: XboxButton) -> some View {
+        let pressed = controller.isPressed(button)
+        return Text(button.label)
+            .font(.callout.weight(.semibold))
+            .frame(width: 32, height: 32)
+            .background(Circle().fill(pressed ? Color.green : Color.secondary.opacity(0.18)))
+            .foregroundStyle(pressed ? .white : .primary)
+    }
+}
+
+struct StickPadView: View {
+    let label: String
+    let x: Int16
+    let y: Int16
+
+    private let diameter: CGFloat = 64
+
+    var body: some View {
+        VStack(spacing: 4) {
+            ZStack {
+                Circle()
+                    .fill(Color.secondary.opacity(0.15))
+                Circle()
+                    .stroke(Color.secondary.opacity(0.35), lineWidth: 1)
+                    .padding(6)
+                Circle()
+                    .fill(Color.accentColor)
+                    .frame(width: 12, height: 12)
+                    .offset(x: offset.width, y: offset.height)
+            }
+            .frame(width: diameter, height: diameter)
+            Text(label)
+                .font(.caption2)
+                .foregroundStyle(.secondary)
+        }
+    }
+
+    // Map the signed 16-bit stick values onto the pad, keeping the dot inside
+    // the ring.
+    private var offset: CGSize {
+        let travel = diameter / 2 - 10
+        return CGSize(
+            width: CGFloat(Double(x) / 32768.0 * travel),
+            height: CGFloat(Double(y) / 32768.0 * travel)
+        )
+    }
+}
+
+struct TriggerBarView: View {
+    let label: String
+    let value: UInt16
+
+    private let barWidth: CGFloat = 56
+
+    var body: some View {
+        VStack(spacing: 4) {
+            ZStack(alignment: .leading) {
+                Color.secondary.opacity(0.18)
+                Color.accentColor
+                    .frame(width: barWidth * fraction, alignment: .leading)
+            }
+            .frame(width: barWidth, height: 6)
+            .clipShape(RoundedRectangle(cornerRadius: 3))
+            Text(label)
+                .font(.caption2)
+                .foregroundStyle(.secondary)
+        }
+    }
+
+    private var fraction: CGFloat {
+        min(max(CGFloat(Double(value) / 1023.0), 0), 1)
+    }
+}
+
+struct ButtonChip: View {
+    let button: XboxButton
+    let pressed: Bool
+
+    var body: some View {
+        Text(button.label)
+            .font(.caption2.weight(.medium))
+            .frame(minWidth: 30, minHeight: 20)
+            .background(pressed ? Color.green : Color.secondary.opacity(0.15))
+            .foregroundStyle(pressed ? .white : .primary)
+            .clipShape(RoundedRectangle(cornerRadius: 4))
+    }
+}