feat: Add FPS toggle shortcut and corresponding input handling in CLI

Signed-off-by: Hans Kokx <hans.d.kokx@gmail.com>

packages/wolf_3d_dart/lib/src/input/cli_input.dart

@@ -12,6 +12,9 @@ class CliInput extends Wolf3dInput {
   /// Keyboard shortcut used by the CLI host to cycle ASCII themes.
   String asciiThemeCycleKey = 't';
 
+  /// Keyboard shortcut used by the CLI host to toggle the FPS counter.
+  String fpsToggleKey = '`';
+
   /// Human-friendly label for [rendererToggleKey] shown in CLI hints.
   String get rendererToggleKeyLabel => _formatShortcutLabel(rendererToggleKey);
 
@@ -19,6 +22,9 @@ class CliInput extends Wolf3dInput {
   String get asciiThemeCycleKeyLabel =>
       _formatShortcutLabel(asciiThemeCycleKey);
 
+  /// Human-friendly label for [fpsToggleKey] shown in CLI hints.
+  String get fpsToggleKeyLabel => _formatShortcutLabel(fpsToggleKey);
+
   /// Returns true when [bytes] triggers the renderer-toggle shortcut.
   bool matchesRendererToggleShortcut(List<int> bytes) =>
       _matchesShortcut(bytes, rendererToggleKey);
@@ -27,6 +33,10 @@ class CliInput extends Wolf3dInput {
   bool matchesAsciiThemeCycleShortcut(List<int> bytes) =>
       _matchesShortcut(bytes, asciiThemeCycleKey);
 
+  /// Returns true when [bytes] triggers the FPS-toggle shortcut.
+  bool matchesFpsToggleShortcut(List<int> bytes) =>
+      _matchesShortcut(bytes, fpsToggleKey);
+
   String _formatShortcutLabel(String key) {
     final String trimmed = key.trim();
     if (trimmed.isEmpty) {