feat(data): add splitting, turns-preflight, merge-order rules to list-handler prompt

Phase 2 can now propose splitting a bundled/blocked task via add_task/add_subtask
instead of forcing it into one description. Phase 3 reports each task's effective
max-turns and asks before queuing a substantial task with a low value. Phase 4
checks Phase 2's file lists for cross-task collisions and may reorder merges with
a stated reason instead of always following brief order.

tests/ClaudeDo.Data.Tests/PromptFilesTests.cs

@@ -87,6 +87,34 @@ public class PromptFilesTests
         Assert.DoesNotContain("whenever you are unsure", d);
     }
 
+    [Fact]
+    public void DefaultFor_merge_helper_allows_splitting_bundled_tasks_in_phase_2()
+    {
+        var d = PromptFiles.DefaultFor(PromptKind.MergeHelper);
+        Assert.Contains("Propose splitting it to the user", d);
+        Assert.Contains("add_task/add_subtask", d);
+        Assert.Contains("do not invent requirements", d);
+    }
+
+    [Fact]
+    public void DefaultFor_merge_helper_checks_effective_max_turns_before_queuing()
+    {
+        var d = PromptFiles.DefaultFor(PromptKind.MergeHelper);
+        Assert.Contains("effective max-turns", d);
+        Assert.Contains("get_list_config", d);
+        Assert.Contains("set_task_config", d);
+        Assert.Contains("get_task_config", d);
+    }
+
+    [Fact]
+    public void DefaultFor_merge_helper_checks_file_collisions_before_merge_order()
+    {
+        var d = PromptFiles.DefaultFor(PromptKind.MergeHelper);
+        Assert.Contains("Default to the order the brief lists them", d);
+        Assert.Contains("tell the user which tasks collide", d);
+        Assert.Contains("NORMAL case, not a failure", d);
+    }
+
     [Fact]
     public void DefaultFor_merge_helper_initial_has_repo_token()
     {