Change over to using command runner for arg parsing

bin/adventofcode2025.dart

@@ -1,29 +1,15 @@
 import 'dart:io';
 
-import 'package:adventofcode2025/day1/main.dart' as day1;
+import 'package:adventofcode2025/day1/command.dart' as day1;
 
-import 'package:args/args.dart';
+import 'package:args/command_runner.dart';
 
 const help = 'help';
 const dayNumber = 'day';
 
 void main(List<String> arguments) {
-  final parser = ArgParser()
-    ..addFlag(help, negatable: false, abbr: 'h')
-    ..addOption(dayNumber, mandatory: true, abbr: "d");
-  var results = parser.parse(arguments);
-
-  if (results.flag(help)) {
-    print(parser.usage);
-    exit(0);
-  }
-
-  var day = results.option(dayNumber);
-
-  switch (day) {
-    case '1':
-      day1.run();
-    default:
-      print("'$day' is not a valid value for option $dayNumber");
-  }
+  var runner =
+      CommandRunner("adventofcode2025", "Advent of Code 2025 solutions")
+        ..addCommand(day1.Day1Command())
+        ..run(arguments);
 }

lib/day1/command.dart

@@ -0,0 +1,21 @@
+import "package:args/command_runner.dart";
+
+class Day1Command extends Command {
+  // The [name] and [description] properties must be defined by every
+  // subclass.
+  final name = "day1";
+  final description = "Run Advent of Code 2025 Day 1";
+
+  Day1Command() {
+    // we can add command specific arguments here.
+    // [argParser] is automatically created by the parent class.
+  }
+
+  // [run] may also return a Future.
+  @override
+  void run() {
+    // [argResults] is set before [run()] is called and contains the flags/options
+    // passed to this command.
+    print(argResults?.rest);
+  }
+}

lib/day1/main.dart

@@ -1,3 +0,0 @@
-void run() {
-  print("Hello World Day 1");
-}