Implement single-owner reconciliation modes

internal/app/run_test.go

@@ -790,6 +790,53 @@ func TestRunNotifiesAfterReplacement(t *testing.T) {
 	}
 }
 
+func TestRunMergeReconciliationRetainsManagedOutput(t *testing.T) {
+	sourceRoot := t.TempDir()
+	destinationRoot := t.TempDir()
+	manifest := testutil.WriteSourceBundle(t, sourceRoot, "", testutil.BundleOptions{
+		Files: []testutil.SourceFile{{Path: "report.md", Data: "# Report\nNew.\n"}},
+	})
+	older := manifest
+	older.Created = older.Created.Add(-time.Hour)
+	defaultManifest := testutil.ValidManifest(testutil.BundleOptions{})
+	older.Files = append([]bundle.ManifestFile(nil), defaultManifest.Files...)
+	older.Digest = bundle.BundleDigest(older.Files)
+	writeDestinationState(t, destinationRoot, "", older)
+	if err := os.WriteFile(filepath.Join(destinationRoot, "report.md"), []byte("old\n"), 0o600); err != nil {
+		t.Fatalf("write old report: %v", err)
+	}
+	if err := os.WriteFile(filepath.Join(destinationRoot, "summary.txt"), []byte("old summary\n"), 0o600); err != nil {
+		t.Fatalf("write old summary: %v", err)
+	}
+	configPath := writeConfigFile(t, `
+pipelines:
+  - id: reports
+    source:
+      backend: local
+      path: `+sourceRoot+`
+    destinations:
+      - id: archive
+        backend: local
+        path: `+destinationRoot+`
+        reconciliation:
+          mode: merge
+`)
+
+	err := Run(context.Background(), RunOptions{ConfigPath: configPath})
+	if err != nil {
+		t.Fatalf("Run() error = %v", err)
+	}
+	testutil.AssertFile(t, filepath.Join(destinationRoot, "report.md"), "# Report\nNew.\n")
+	testutil.AssertFile(t, filepath.Join(destinationRoot, "summary.txt"), "old summary\n")
+	destinationState := readStateFile(t, filepath.Join(destinationRoot, storage.StateFileName))
+	if got, want := destinationState.Reconciliation.Mode, config.ReconciliationModeMerge; got != want {
+		t.Fatalf("reconciliation mode = %q, want %q", got, want)
+	}
+	if got, want := len(destinationState.Outputs), 2; got != want {
+		t.Fatalf("state output count = %d, want %d", got, want)
+	}
+}
+
 func TestRunJSONIncludesGeneratedOutputMetadata(t *testing.T) {
 	sourceRoot := t.TempDir()
 	destinationRoot := t.TempDir()