feat(installer): add InstallManifest + json-backed store

src/ClaudeDo.Installer/Core/InstallManifest.cs

@@ -0,0 +1,48 @@
+using System.IO;
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace ClaudeDo.Installer.Core;
+
+public sealed record InstallManifest(
+    string Version,
+    string InstallDir,
+    string WorkerDir,
+    DateTimeOffset InstalledAt);
+
+public static class InstallManifestStore
+{
+    public const string FileName = "install.json";
+
+    private static readonly JsonSerializerOptions JsonOptions = new()
+    {
+        WriteIndented = true,
+        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
+        DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull,
+    };
+
+    public static string ManifestPath(string installDir) => Path.Combine(installDir, FileName);
+
+    public static InstallManifest? TryRead(string installDir)
+    {
+        var path = ManifestPath(installDir);
+        if (!File.Exists(path)) return null;
+
+        try
+        {
+            var json = File.ReadAllText(path);
+            return JsonSerializer.Deserialize<InstallManifest>(json, JsonOptions);
+        }
+        catch
+        {
+            return null;
+        }
+    }
+
+    public static void Write(string installDir, InstallManifest manifest)
+    {
+        Directory.CreateDirectory(installDir);
+        var json = JsonSerializer.Serialize(manifest, JsonOptions);
+        File.WriteAllText(ManifestPath(installDir), json);
+    }
+}

tests/ClaudeDo.Installer.Tests/InstallManifestStoreTests.cs

@@ -0,0 +1,66 @@
+using System.IO;
+using ClaudeDo.Installer.Core;
+
+namespace ClaudeDo.Installer.Tests;
+
+public sealed class InstallManifestStoreTests : IDisposable
+{
+    private readonly string _tempDir;
+
+    public InstallManifestStoreTests()
+    {
+        _tempDir = Path.Combine(Path.GetTempPath(), "ClaudeDoInstallerTests-" + Guid.NewGuid().ToString("N"));
+        Directory.CreateDirectory(_tempDir);
+    }
+
+    public void Dispose()
+    {
+        try { Directory.Delete(_tempDir, recursive: true); } catch { /* best effort */ }
+    }
+
+    [Fact]
+    public void TryRead_ReturnsNull_WhenFileMissing()
+    {
+        var result = InstallManifestStore.TryRead(_tempDir);
+        Assert.Null(result);
+    }
+
+    [Fact]
+    public void Write_Then_Read_RoundTripsAllFields()
+    {
+        var manifest = new InstallManifest(
+            Version: "0.2.0",
+            InstallDir: _tempDir,
+            WorkerDir: Path.Combine(_tempDir, "worker"),
+            InstalledAt: new DateTimeOffset(2026, 4, 15, 12, 34, 56, TimeSpan.Zero));
+
+        InstallManifestStore.Write(_tempDir, manifest);
+
+        var round = InstallManifestStore.TryRead(_tempDir);
+        Assert.NotNull(round);
+        Assert.Equal("0.2.0", round!.Version);
+        Assert.Equal(manifest.InstallDir, round.InstallDir);
+        Assert.Equal(manifest.WorkerDir, round.WorkerDir);
+        Assert.Equal(manifest.InstalledAt, round.InstalledAt);
+    }
+
+    [Fact]
+    public void Write_CreatesInstallDir_IfMissing()
+    {
+        var nested = Path.Combine(_tempDir, "nested");
+        Assert.False(Directory.Exists(nested));
+
+        InstallManifestStore.Write(nested, new InstallManifest(
+            "0.0.1", nested, Path.Combine(nested, "worker"), DateTimeOffset.UtcNow));
+
+        Assert.True(File.Exists(Path.Combine(nested, "install.json")));
+    }
+
+    [Fact]
+    public void TryRead_ReturnsNull_WhenJsonMalformed()
+    {
+        File.WriteAllText(Path.Combine(_tempDir, "install.json"), "{ not json");
+        var result = InstallManifestStore.TryRead(_tempDir);
+        Assert.Null(result);
+    }
+}