fix(worker-tests): pin LogRingBuffer clock in Does_not_throw_when_detached

The test built the buffer with the real DateTime.UtcNow clock but emitted
an event with the file's fixed EvtTime timestamp (2026-06-23). As real
time drifted more than the 1h window past that fixed timestamp, the
just-appended record was evicted inside the same Append call, before
Snapshot() ran. BroadcastLogSink.Emit itself buffers unconditionally
regardless of attach state, so this was a test bug, not a sink bug. Pin
the buffer's clock to EvtTime, matching every sibling test's NewSink setup.

tests/ClaudeDo.Worker.Tests/Logging/BroadcastLogSinkTests.cs

@@ -98,7 +98,7 @@ public class BroadcastLogSinkTests
     [Fact]
     public void Does_not_throw_when_detached()
     {
-        var buffer = new LogRingBuffer(TimeSpan.FromHours(1));
+        var buffer = new LogRingBuffer(TimeSpan.FromHours(1), utcNow: () => EvtTime.UtcDateTime);
         var sink = new BroadcastLogSink(buffer);
         sink.Emit(Evt(LogEventLevel.Error, "no subscriber"));