Keep creation as a living DAG and archive playable products separately.

Opening accept no longer locks the graph; session.json stays creation-only while play starts from an instance snapshot. Sidebar products nest run saves, and play reading fills the feed at a denser type size.

Co-authored-by: Cursor <cursoragent@cursor.com>

tests/opening-seal.test.ts

@@ -37,6 +37,13 @@ describe("opening-seal", () => {
         outputTags: ["输出.开场白"],
       }),
     ).toBe(true);
+    expect(
+      isOpeningSealArtifact({
+        workerId: "design-step",
+        stepId: "开场白与开场变量",
+        outputTags: ["artifact.flat.v1"],
+      }),
+    ).toBe(true);
     expect(
       isOpeningSealArtifact({
         workerId: "design-step",