feat(worker): expose merge-helper launch spec over hub + client

src/ClaudeDo.Worker/Hub/WorkerHub.cs

@@ -676,6 +676,16 @@ public sealed class WorkerHub : Microsoft.AspNetCore.SignalR.Hub
         return _interactiveLaunchSpec.BuildForDirectoryAsync(directory, Context.ConnectionAborted);
     });
 
+    // Builds the launch spec for an embedded ConPTY "merge helper" session that drives the given
+    // tasks to a merged/Done state via the mcp__claudedo__* tools. listId scopes the brief label
+    // and cwd to that list; null means all lists.
+    public Task<LaunchSpec> GetMergeHelperLaunchSpec(string[] taskIds, string? listId) => HubGuard(() =>
+    {
+        if (_interactiveLaunchSpec is null)
+            throw new InvalidOperationException("Interactive launch spec service is not configured.");
+        return _interactiveLaunchSpec.BuildForMergeHelperAsync(taskIds, listId, Context.ConnectionAborted);
+    });
+
     // Starts a planning session (worktree + prompt files + token, task -> Planning) and returns
     // the launch spec for an embedded ConPTY planning terminal -- the ConPTY replacement for
     // StartPlanningSessionAsync's external wt window. On any spec-build failure the just-started