feat(core): add PluginManifest json parsing

tests/AcDream.Core.Tests/Plugins/PluginManifestTests.cs

@@ -0,0 +1,62 @@
+using AcDream.Core.Plugins;
+
+namespace AcDream.Core.Tests.Plugins;
+
+public class PluginManifestTests
+{
+    [Fact]
+    public void Parse_ValidManifest_ReturnsManifest()
+    {
+        const string json = """
+        {
+          "id": "acdream.smoke",
+          "displayName": "Smoke Test",
+          "version": "0.1.0",
+          "entryDll": "AcDream.Plugins.Smoke.dll",
+          "apiVersion": 1
+        }
+        """;
+
+        var manifest = PluginManifest.Parse(json);
+
+        Assert.Equal("acdream.smoke", manifest.Id);
+        Assert.Equal("Smoke Test", manifest.DisplayName);
+        Assert.Equal("0.1.0", manifest.Version);
+        Assert.Equal("AcDream.Plugins.Smoke.dll", manifest.EntryDll);
+        Assert.Equal(1, manifest.ApiVersion);
+    }
+
+    [Fact]
+    public void Parse_MissingRequiredField_Throws()
+    {
+        const string json = """
+        { "id": "x", "version": "0.1.0", "entryDll": "x.dll", "apiVersion": 1 }
+        """;
+
+        var ex = Assert.Throws<PluginManifestException>(() => PluginManifest.Parse(json));
+        Assert.Contains("displayName", ex.Message);
+    }
+
+    [Fact]
+    public void Parse_MalformedJson_Throws()
+    {
+        Assert.Throws<PluginManifestException>(() => PluginManifest.Parse("{ not json"));
+    }
+
+    [Fact]
+    public void Parse_EmptyDependencies_DefaultsToEmptyList()
+    {
+        const string json = """
+        {
+          "id": "x",
+          "displayName": "X",
+          "version": "0.1.0",
+          "entryDll": "x.dll",
+          "apiVersion": 1
+        }
+        """;
+
+        var manifest = PluginManifest.Parse(json);
+        Assert.Empty(manifest.Dependencies);
+    }
+}