feat(ui): highlight user chat messages + opt-in interrupt (stop) button

LogKindForegroundConverter drives the log message foreground via a local
binding (beats the dim local value), so user messages render in the accent
color instead of vanishing into the transcript. Adds a small stop (Icon.Stop)
button next to Send in both composers (SessionTerminalView + WorkConsole) wired
to InterruptInteractiveCommand → InterruptInteractiveSessionAsync. Adds
session.composer.interrupt (en/de).

tests/ClaudeDo.Ui.Tests/ViewModels/TaskMonitorViewModelTests.cs

@@ -297,4 +297,18 @@ public class TaskMonitorViewModelTests : IDisposable
         Assert.Equal(LogKind.User, vm.Log[0].Kind);
         Assert.Equal("do the thing", vm.Log[0].Text);
     }
+
+    [Fact]
+    public async Task InterruptInteractiveCommand_WhenLive_RecordsOneCall()
+    {
+        var worker = new FakeWorker();
+        using var vm = Build(worker);
+        vm.SetTaskId("t1");
+        worker.RaiseInteractiveStarted("t1");
+
+        await vm.InterruptInteractiveCommand.ExecuteAsync(null);
+
+        Assert.Single(worker.InterruptedInteractive);
+        Assert.Equal("t1", worker.InterruptedInteractive[0]);
+    }
 }