Keyboard and Xbox-gamepad input drive the panel

New input pipeline: sources feed an InputRouter (VRio.Core.Input) that
calls the same VRioDevice press/release/axis entry points the mouse
canvas uses, so routed input is indistinguishable on the wire.

- Bindings live in %APPDATA%\vRIO\bindings.txt (plain text, commented
  defaults written on first run; Reload/Edit buttons in the new Input
  group). Keys and pad buttons press any RIO address, momentary or
  toggle; axes bind in normalized units of each axis realistic travel
  window with deflect (spring-back), rate (position holds), deadzone,
  and invert options - RioAxisRange supplies the wire signs.
- Router suppresses key auto-repeat, edge-detects pad buttons, and
  hold-counts per address so overlapping sources press once and
  release last; axes only write when the composed value changes, so
  mouse drags keep working while sources idle.
- Xbox pad via a zero-dependency XInput P/Invoke poller (xinput1_4,
  fallback xinput9_1_0), throttled rescan while disconnected.
- MainForm intercepts bound keys in ProcessCmdKey so arrows/space
  reach the panel instead of moving focus; keys release on focus
  loss; center-axes and host ResetRequest reset the rate integrators.
- Canvas highlights router-held addresses like clicks.
- Defaults: arrows=stick, W/S=throttle, Q/E=pedals, numpad=internal
  keypad, IJKL/Space=hat+main; pad left stick/triggers/right stick =
  stick/pedals/throttle-rate, ABXY/dpad/shoulders = named buttons.

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

src/VRio.Core/Input/PadState.cs

@@ -0,0 +1,76 @@
+namespace VRio.Core.Input;
+
+/// <summary>
+/// Gamepad button flags, bit-for-bit the XInput <c>wButtons</c> mask so the
+/// App-side poller can cast the native value straight through.
+/// </summary>
+[Flags]
+public enum PadButtons : ushort
+{
+    None = 0,
+    DPadUp = 0x0001,
+    DPadDown = 0x0002,
+    DPadLeft = 0x0004,
+    DPadRight = 0x0008,
+    Start = 0x0010,
+    Back = 0x0020,
+    LeftThumb = 0x0040,
+    RightThumb = 0x0080,
+    LeftShoulder = 0x0100,
+    RightShoulder = 0x0200,
+    A = 0x1000,
+    B = 0x2000,
+    X = 0x4000,
+    Y = 0x8000,
+}
+
+/// <summary>A gamepad analog control usable as a binding source.</summary>
+public enum PadAxis
+{
+    LeftStickX,
+    LeftStickY,
+    RightStickX,
+    RightStickY,
+    LeftTrigger,
+    RightTrigger,
+}
+
+/// <summary>
+/// One normalized gamepad snapshot: sticks −1..+1 (up/right positive),
+/// triggers 0..1. The default value is "pad at rest / no pad connected".
+/// </summary>
+public readonly struct PadState
+{
+    public PadState(PadButtons buttons,
+        float leftStickX, float leftStickY, float rightStickX, float rightStickY,
+        float leftTrigger, float rightTrigger)
+    {
+        Buttons = buttons;
+        LeftStickX = leftStickX;
+        LeftStickY = leftStickY;
+        RightStickX = rightStickX;
+        RightStickY = rightStickY;
+        LeftTrigger = leftTrigger;
+        RightTrigger = rightTrigger;
+    }
+
+    public PadButtons Buttons { get; }
+    public float LeftStickX { get; }
+    public float LeftStickY { get; }
+    public float RightStickX { get; }
+    public float RightStickY { get; }
+    public float LeftTrigger { get; }
+    public float RightTrigger { get; }
+
+    /// <summary>Value of one analog control.</summary>
+    public float Axis(PadAxis axis) => axis switch
+    {
+        PadAxis.LeftStickX => LeftStickX,
+        PadAxis.LeftStickY => LeftStickY,
+        PadAxis.RightStickX => RightStickX,
+        PadAxis.RightStickY => RightStickY,
+        PadAxis.LeftTrigger => LeftTrigger,
+        PadAxis.RightTrigger => RightTrigger,
+        _ => 0f,
+    };
+}