feat(i18n): seed en.json and wire locale copy to app output

tests/ClaudeDo.Localization.Tests/EnJsonCoverageTests.cs

@@ -0,0 +1,37 @@
+using ClaudeDo.Localization;
+
+namespace ClaudeDo.Localization.Tests;
+
+public class EnJsonCoverageTests
+{
+    private static string LocalesDir()
+    {
+        var dir = AppContext.BaseDirectory;
+        while (dir is not null)
+        {
+            var candidate = Path.Combine(dir, "src", "ClaudeDo.Localization", "locales");
+            if (Directory.Exists(candidate)) return candidate;
+            dir = Path.GetDirectoryName(dir);
+        }
+        throw new DirectoryNotFoundException("Could not locate src/ClaudeDo.Localization/locales");
+    }
+
+    [Fact]
+    public void Every_locale_has_same_keys_as_english()
+    {
+        var store = LocaleStore.Load(LocalesDir());
+        Assert.True(store.TryGet("en", out var en));
+        var enKeys = en!.Strings.Keys.ToHashSet();
+
+        foreach (var locale in store.Available)
+        {
+            var keys = locale.Strings.Keys.ToHashSet();
+            var missing = enKeys.Except(keys).OrderBy(k => k).ToList();
+            var extra = keys.Except(enKeys).OrderBy(k => k).ToList();
+            Assert.True(missing.Count == 0,
+                $"Locale '{locale.Code}' missing keys: {string.Join(", ", missing)}");
+            Assert.True(extra.Count == 0,
+                $"Locale '{locale.Code}' has extra keys not in en.json: {string.Join(", ", extra)}");
+        }
+    }
+}