feat(i18n): add ClaudeDo.Localization project with nested-JSON locale parser

tests/ClaudeDo.Localization.Tests/ClaudeDo.Localization.Tests.csproj

@@ -0,0 +1,20 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <IsPackable>false</IsPackable>
+    <IsTestProject>true</IsTestProject>
+  </PropertyGroup>
+  <ItemGroup>
+    <Using Include="Xunit" />
+  </ItemGroup>
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
+    <PackageReference Include="xunit" Version="2.9.3" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="3.0.1" />
+  </ItemGroup>
+  <ItemGroup>
+    <ProjectReference Include="../../src/ClaudeDo.Localization/ClaudeDo.Localization.csproj" />
+  </ItemGroup>
+</Project>

tests/ClaudeDo.Localization.Tests/LocaleJsonTests.cs

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+using ClaudeDo.Localization;
+
+namespace ClaudeDo.Localization.Tests;
+
+public class LocaleJsonTests
+{
+    private const string Sample = """
+    {
+      "metadata": { "code": "en", "name": "English" },
+      "settings": { "save": "Save", "general": { "model": "Model" } },
+      "tasks": { "addPlaceholder": "Add a task" }
+    }
+    """;
+
+    [Fact]
+    public void Parse_reads_metadata()
+    {
+        var f = LocaleJson.Parse(Sample);
+        Assert.Equal("en", f.Code);
+        Assert.Equal("English", f.Name);
+    }
+
+    [Fact]
+    public void Parse_flattens_nested_keys_to_dot_paths()
+    {
+        var f = LocaleJson.Parse(Sample);
+        Assert.Equal("Save", f.Strings["settings.save"]);
+        Assert.Equal("Model", f.Strings["settings.general.model"]);
+        Assert.Equal("Add a task", f.Strings["tasks.addPlaceholder"]);
+    }
+
+    [Fact]
+    public void Parse_excludes_metadata_from_strings()
+    {
+        var f = LocaleJson.Parse(Sample);
+        Assert.False(f.Strings.ContainsKey("metadata.code"));
+    }
+}