Wait for packet echoes and send only changed packets

The keyboard echoes each colour packet back; wait for that echo before
sending the next one, like OpenRGB's EVision driver, instead of firing all
packets back to back. Skip packets whose colours did not change and resend
the whole frame every 500 ms so the keyboard stays under plugin control.
Add a passive listener tool for the echoes.

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

tools/evision_listen.ps1

@@ -0,0 +1,35 @@
+# Passively reads input reports from the EVision RGB endpoint for a few seconds
+param([double]$Seconds = 2, [string]$Match = 'VID_320F&PID_502A&MI_01&COL04')
+Add-Type @"
+using System;
+using System.IO;
+using System.Runtime.InteropServices;
+using Microsoft.Win32.SafeHandles;
+public static class EVL {
+  [DllImport("kernel32.dll", SetLastError=true, CharSet=CharSet.Unicode)]
+  public static extern SafeFileHandle CreateFile(string n, uint a, uint s, IntPtr sa, uint c, uint f, IntPtr t);
+  public static string Listen(string path, int ms) {
+    var h = CreateFile(path, 0x80000000, 3, IntPtr.Zero, 3, 0x40000000, IntPtr.Zero);
+    if (h.IsInvalid) return "open failed " + Marshal.GetLastWin32Error();
+    var sb = new System.Text.StringBuilder();
+    var counts = new System.Collections.Generic.Dictionary<string,int>();
+    using (var fs = new FileStream(h, FileAccess.Read, 64, true)) {
+      var end = DateTime.Now.AddMilliseconds(ms); int n = 0;
+      while (DateTime.Now < end) {
+        var buf = new byte[64];
+        var t = fs.ReadAsync(buf, 0, 64);
+        if (!t.Wait(end - DateTime.Now > TimeSpan.Zero ? end - DateTime.Now : TimeSpan.Zero)) break;
+        n++;
+        var key = BitConverter.ToString(buf, 0, 8);
+        counts[key] = counts.ContainsKey(key) ? counts[key] + 1 : 1;
+      }
+      sb.AppendLine("reports: " + n);
+      foreach (var kv in counts) sb.AppendLine(kv.Value + "x  " + kv.Key);
+    }
+    return sb.ToString();
+  }
+}
+"@
+$dev = Get-PnpDevice -PresentOnly -Class HIDClass | Where-Object { $_.InstanceId -match [regex]::Escape($Match) } | Select-Object -First 1
+$path = '\\?\' + ($dev.InstanceId -replace '\\','#') + '#{4d1e55b2-f16f-11cf-88cb-001111000030}'
+[EVL]::Listen($path, [int]($Seconds * 1000))