fix(tests): stop Ui.Tests order-dependent flakiness on shared Loc.Current

Loc.Current (src/ClaudeDo.Ui/Localization/Loc.cs) is a process-wide mutable
static; which localizer is active depended on xUnit's parallel test
scheduling. Ui.Tests: disable collection parallelization (cheap, pure VM
suite) and install the real localizer in a module initializer so no test
can ever observe the uninitialized key-echo default. Worker.Tests: install
the same module initializer but leave parallelization on — disabling it
measured a 27% wall-clock regression on its real-SQLite/git suite, and the
initializer alone already removes the race. AgentConfigEditorViewModelTests
now installs its own localizer instead of relying on ambient state.

tests/ClaudeDo.Worker.Tests/TestSetup.cs

@@ -1,4 +1,6 @@
 using System.Runtime.CompilerServices;
+using ClaudeDo.Localization;
+using ClaudeDo.Ui.Localization;
 using ClaudeDo.Ui.Services;
 
 namespace ClaudeDo.Worker.Tests;
@@ -16,4 +18,20 @@ internal static class TestSetup
         var path = Path.Combine(Path.GetTempPath(), "claudedo-worker-tests", $"operation-timing-{Environment.ProcessId}.ndjson");
         OperationTiming.Shared = new OperationTiming(path);
     }
+
+    // Installs the real localizer before any test runs, mirroring ClaudeDo.Ui.Tests' TestSetup,
+    // so a UiVm test that reads Loc.T without setting up its own localizer doesn't depend on
+    // ambient state left by whichever test class happened to run first. Deliberately does NOT
+    // also disable test parallelization here (unlike Ui.Tests) — measured 14m49s -> 18m46s
+    // (+27%) on this project's real-SQLite/git suite, too costly for a test-only ordering issue
+    // that the module initializer alone already closes.
+    [ModuleInitializer]
+    internal static void InstallRealLocalizer()
+    {
+        var dir = AppContext.BaseDirectory;
+        while (dir is not null && !Directory.Exists(Path.Combine(dir, "src", "ClaudeDo.Localization", "locales")))
+            dir = Path.GetDirectoryName(dir);
+        Loc.Current = new Localizer(
+            LocaleStore.Load(Path.Combine(dir!, "src", "ClaudeDo.Localization", "locales")), "en");
+    }
 }