Clean up the formatting a little and add duration to lap

lib/main.dart

@@ -84,19 +84,39 @@ class _MyHomePageState extends State<MyHomePage> {
     if (_isRunning) {
       final now = DateTime.now();
       setState(() {
-        _laps.add(now.toIso8601String());
+        // Store both timestamp and formatted duration for this lap
+        _laps.add('${now.toIso8601String()} - ${_formatDuration(_elapsedTime)}');
       });
     }
   }
 
   String _formatDuration(Duration duration) {
-    // Format the duration as ISO 8601 duration format: PT[hours]H[minutes]M[seconds]S
+    // Format the duration as ISO 8601 duration format without 0 values
     final hours = duration.inHours;
     final minutes = duration.inMinutes.remainder(60);
     final seconds = duration.inSeconds.remainder(60);
-    final milliseconds = duration.inMilliseconds.remainder(1000);
     
-    return 'PT${hours}H${minutes}M${seconds}.${milliseconds}S';
+    // Round milliseconds to nearest 100ms for more consistent display
+    // This helps avoid floating point inconsistencies (0.201, 0.301, etc.)
+    final milliseconds = ((duration.inMilliseconds % 1000) / 100).round() * 100;
+    final formattedMs = (milliseconds ~/ 100).toString();
+    
+    // Start with PT prefix
+    String result = 'PT';
+    
+    // Only add parts that are non-zero (except if everything is zero, then show 0S)
+    if (hours > 0) {
+      result += '${hours}H';
+    }
+    
+    if (minutes > 0 || hours > 0) {
+      result += '${minutes}M';
+    }
+    
+    // Always include seconds with a single decimal place (tenth of a second)
+    result += '${seconds}.${formattedMs}S';
+    
+    return result;
   }
 
   void _handleKeyEvent(RawKeyEvent event) {
@@ -152,9 +172,15 @@ class _MyHomePageState extends State<MyHomePage> {
                 style: Theme.of(context).textTheme.headlineSmall,
               ),
               const SizedBox(height: 10),
-              Text(
-                _formatDuration(_elapsedTime),
-                style: Theme.of(context).textTheme.headlineMedium,
+              Container(
+                width: 300, // Fixed width container to prevent "flashing"
+                alignment: Alignment.center,
+                child: Text(
+                  _formatDuration(_elapsedTime),
+                  style: Theme.of(context).textTheme.headlineMedium?.copyWith(
+                    fontFamily: 'monospace', // Use monospaced font for fixed-width characters
+                  ),
+                ),
               ),
               const SizedBox(height: 30),
               Row(