Refactor game loop to await start and enhance Sixel rasterizer terminal support detection

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

apps/wolf_3d_cli/lib/cli_game_loop.dart

@@ -9,7 +9,13 @@ class CliGameLoop {
   CliGameLoop({
     required this.engine,
     required this.onExit,
-  }) : input = CliInput(),
+  }) : input = engine.input is CliInput
+           ? engine.input as CliInput
+           : throw ArgumentError.value(
+               engine.input,
+               'engine.input',
+               'CliGameLoop requires a CliInput instance.',
+             ),
        primaryRasterizer = SixelRasterizer(),
        secondaryRasterizer = AsciiRasterizer(isTerminal: true) {
     _rasterizer = primaryRasterizer;
@@ -22,23 +28,37 @@ class CliGameLoop {
   final void Function(int code) onExit;
 
   final Stopwatch _stopwatch = Stopwatch();
+  final Stream<List<int>> _stdinStream = stdin.asBroadcastStream();
   late CliRasterizer _rasterizer;
   StreamSubscription<List<int>>? _stdinSubscription;
   Timer? _timer;
   bool _isRunning = false;
   Duration _lastTick = Duration.zero;
 
-  void start() {
+  Future<void> start() async {
     if (_isRunning) {
       return;
     }
 
-    stdin.echoMode = false;
-    stdin.lineMode = false;
+    if (primaryRasterizer is SixelRasterizer) {
+      final sixel = primaryRasterizer as SixelRasterizer;
+      sixel.isSixelSupported = await SixelRasterizer.checkTerminalSixelSupport(
+        inputStream: _stdinStream,
+      );
+    }
+
+    if (stdin.hasTerminal) {
+      try {
+        stdin.echoMode = false;
+        stdin.lineMode = false;
+      } catch (_) {
+        // Keep running without raw mode when stdin is not mutable.
+      }
+    }
 
     stdout.write('\x1b[?25l\x1b[2J');
 
-    _stdinSubscription = stdin.listen(_handleInput);
+    _stdinSubscription = _stdinStream.listen(_handleInput);
     _stopwatch.start();
     _timer = Timer.periodic(const Duration(milliseconds: 33), _tick);
     _isRunning = true;
@@ -59,8 +79,12 @@ class CliGameLoop {
     }
 
     if (stdin.hasTerminal) {
-      stdin.echoMode = true;
-      stdin.lineMode = true;
+      try {
+        stdin.echoMode = true;
+        stdin.lineMode = true;
+      } catch (_) {
+        // Ignore cleanup failures if stdin is no longer a mutable TTY.
+      }
     }
 
     if (stdout.hasTerminal) {