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/InputBindings.cs

@@ -0,0 +1,69 @@
+using VRio.Core.Device;
+
+namespace VRio.Core.Input;
+
+/// <summary>
+/// How a key drives an axis: <see cref="Deflect"/> holds the axis at the
+/// binding's value while the key is down and springs back when released
+/// (stick, pedals); <see cref="Rate"/> walks the axis by value-per-second
+/// while held and the position sticks (throttle).
+/// </summary>
+public enum KeyAxisMode
+{
+    Deflect,
+    Rate,
+}
+
+/// <summary>A keyboard key pressing a RIO input address.</summary>
+/// <param name="Key">Key name as the host reports it (System.Windows.Forms
+/// Keys.ToString(): "W", "Up", "NumPad1", …); matched case-insensitively.</param>
+/// <param name="Address">RIO input address (button 0x00–0x47 or keypad 0x50–0x6F).</param>
+/// <param name="Toggle">Latch on press instead of momentary press/release.</param>
+public sealed record KeyButtonBinding(string Key, int Address, bool Toggle);
+
+/// <summary>
+/// A keyboard key driving a RIO axis in normalized units, where 1 is the
+/// axis' full realistic travel (<see cref="RioAxisRange.Full"/> carries the
+/// wire sign, so bindings never deal with the throttle's negative direction).
+/// </summary>
+/// <param name="Value">Deflect: the normalized position held while the key is
+/// down. Rate: normalized units per second, signed.</param>
+public sealed record KeyAxisBinding(string Key, RioAxis Axis, KeyAxisMode Mode, float Value);
+
+/// <summary>A gamepad button pressing a RIO input address.</summary>
+public sealed record PadButtonBinding(PadButtons Button, int Address, bool Toggle);
+
+/// <summary>
+/// A gamepad analog control driving a RIO axis. With <paramref name="Rate"/>
+/// zero the (deadzoned, optionally inverted) pad value maps directly to the
+/// normalized axis position; with a positive rate the pad value is a speed —
+/// the axis integrates by value × rate per second and holds (throttle-style).
+/// </summary>
+public sealed record PadAxisBinding(PadAxis Source, RioAxis Axis, bool Invert, float Deadzone, float Rate);
+
+/// <summary>An immutable set of input bindings (one parsed profile file).</summary>
+public sealed class BindingProfile
+{
+    public static readonly BindingProfile Empty = new(
+        Array.Empty<KeyButtonBinding>(), Array.Empty<KeyAxisBinding>(),
+        Array.Empty<PadButtonBinding>(), Array.Empty<PadAxisBinding>());
+
+    public BindingProfile(
+        IReadOnlyList<KeyButtonBinding> keyButtons,
+        IReadOnlyList<KeyAxisBinding> keyAxes,
+        IReadOnlyList<PadButtonBinding> padButtons,
+        IReadOnlyList<PadAxisBinding> padAxes)
+    {
+        KeyButtons = keyButtons;
+        KeyAxes = keyAxes;
+        PadButtons = padButtons;
+        PadAxes = padAxes;
+    }
+
+    public IReadOnlyList<KeyButtonBinding> KeyButtons { get; }
+    public IReadOnlyList<KeyAxisBinding> KeyAxes { get; }
+    public IReadOnlyList<PadButtonBinding> PadButtons { get; }
+    public IReadOnlyList<PadAxisBinding> PadAxes { get; }
+
+    public int Count => KeyButtons.Count + KeyAxes.Count + PadButtons.Count + PadAxes.Count;
+}