feat(refine): add RefineRunner, prompt/args helper, and interfaces

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/ClaudeDo.Worker/Refine/Interfaces/IRefineRunner.cs

@@ -0,0 +1,8 @@
+namespace ClaudeDo.Worker.Refine;
+
+public interface IRefineRunner
+{
+    Task<RefineRunOutcome> RefineAsync(string taskId, CancellationToken ct);
+}
+
+public sealed record RefineRunOutcome(bool Success, string Message);