feat(data): add merge-helper prompt templates

tests/ClaudeDo.Data.Tests/PromptFilesTests.cs

@@ -43,4 +43,41 @@ public class PromptFilesTests
     {
         Assert.EndsWith("planning-system.md", PromptFiles.PathFor(PromptKind.Planning));
     }
+
+    [Fact]
+    public void PathFor_merge_helper_kinds_map_to_their_files()
+    {
+        Assert.EndsWith("merge-helper-system.md", PromptFiles.PathFor(PromptKind.MergeHelper));
+        Assert.EndsWith("merge-helper-initial.md", PromptFiles.PathFor(PromptKind.MergeHelperInitial));
+    }
+
+    [Fact]
+    public void DefaultFor_merge_helper_is_non_empty_and_mentions_the_merge_tools()
+    {
+        var d = PromptFiles.DefaultFor(PromptKind.MergeHelper);
+        Assert.False(string.IsNullOrWhiteSpace(d));
+        Assert.Contains("review_task", d);
+        Assert.Contains("continue_merge", d);
+    }
+
+    [Fact]
+    public void DefaultFor_merge_helper_initial_has_scope_and_tasks_tokens()
+    {
+        var d = PromptFiles.DefaultFor(PromptKind.MergeHelperInitial);
+        Assert.False(string.IsNullOrWhiteSpace(d));
+        Assert.Contains("{scope}", d);
+        Assert.Contains("{tasks}", d);
+    }
+
+    [Fact]
+    public void RenderTemplate_merge_helper_initial_substitutes_scope_and_tasks()
+    {
+        var outp = PromptFiles.RenderTemplate(
+            PromptFiles.DefaultFor(PromptKind.MergeHelperInitial),
+            new Dictionary<string, string> { ["scope"] = "All lists", ["tasks"] = "- [Idle] T1" });
+        Assert.Contains("Scope: All lists", outp);
+        Assert.Contains("- [Idle] T1", outp);
+        Assert.DoesNotContain("{scope}", outp);
+        Assert.DoesNotContain("{tasks}", outp);
+    }
 }