feat(a1): CLI (run/trace) + vm0.py --trace + per-scene differential test (A1 green)

C# VM is byte-identical to vm0.py across all 297 SC/SP scenes (offsets+halt+steps);
RECOVER passes; SC0000 = 27994 steps / 186 lines matching the Python prototype.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

engine/Age.Cli/Program.cs

@@ -1,2 +1,37 @@
-// See https://aka.ms/new-console-template for more information
-Console.WriteLine("Hello, World!");
+using System.Text.Json;
+using System.Text.RegularExpressions;
+using Age.Engine.Hosting;
+using Age.Engine.Sys4;
+using Age.Engine.Vm;
+
+var table = OpcodeTableJson.Load(Paths.OpcodesJson);
+
+if (args.Length == 0) { Console.WriteLine("usage: run <file> | trace <out.json>"); return 1; }
+
+if (args[0] == "run")
+{
+    var script = Sys4Loader.Load(args[1], table);
+    var vm = new VirtualMachine(script, table, new CaptureHost());
+    vm.Run();
+    Console.WriteLine($"{Path.GetFileName(args[1])}: {vm.Steps} steps, {vm.Emitted.Count} show-text (halt: {vm.HaltReason})");
+    foreach (var (off, text) in vm.Emitted.Take(20)) Console.WriteLine($"  [{off:x}] {text}");
+    return 0;
+}
+
+if (args[0] == "trace")
+{
+    var scene = new Regex(@"^S[CP]\d{4}\.BIN$");
+    var scripts = Paths.Scripts();
+    var trace = new SortedDictionary<string, object>(StringComparer.Ordinal);
+    foreach (var name in scripts.Keys.Where(n => scene.IsMatch(n)).OrderBy(n => n, StringComparer.Ordinal))
+    {
+        var vm = new VirtualMachine(Sys4Loader.Load(scripts[name], table), table, new CaptureHost());
+        vm.Run();
+        trace[name] = new { offsets = vm.Emitted.Select(e => e.Offset).ToArray(), halt = vm.HaltReason, steps = vm.Steps };
+    }
+    File.WriteAllText(args[1], JsonSerializer.Serialize(trace,
+        new JsonSerializerOptions { Encoder = System.Text.Encodings.Web.JavaScriptEncoder.UnsafeRelaxedJsonEscaping }));
+    Console.WriteLine($"trace: {trace.Count} scenes -> {args[1]}");
+    return 0;
+}
+Console.WriteLine("unknown command"); return 1;