CE-WP-0006/0007: Capture view polish, workplans, and UX refinements

- Blob URL stability, scroll centre, strip-only visual guide
- Focus-gated linking, unlink clears overlay, field badge tooltips
- Capture layout (viewer centre), grey guide lines, Add field button
- Workplans CE-WP-0006 (done) and CE-WP-0007 (T01-T09 done, T10-T12 todo)
- Integration tests and viewer-url helpers

src/engine/persistence.test.ts

@@ -7,6 +7,7 @@ import {
   createEngine,
   restoreFromStorage,
   restoreSnapshot,
+  sanitizeDocumentForPersistence,
   type Engine,
   type EngineEvent,
   type EngineSnapshot,
@@ -170,6 +171,31 @@ describe("restoreFromStorage", () => {
     expect(dst.documents.list()).toHaveLength(1);
   });
 
+  it("strips blob: URIs from persisted documents", () => {
+    const engine = createEngine();
+    const docId = "doc_blob" as DocumentId;
+    engine.documents.register({
+      document: {
+        id: docId,
+        mediaType: "application/pdf",
+        title: "upload.pdf",
+        uri: "blob:http://localhost/dead",
+        createdAt: "2026-06-07T00:00:00.000Z",
+        updatedAt: "2026-06-07T00:00:00.000Z",
+      },
+      representation: fakeDocAndRep("blob").representation,
+    });
+    const snap = captureSnapshot(engine);
+    expect(snap.documents[0]?.uri).toBeUndefined();
+    expect(sanitizeDocumentForPersistence({
+      id: docId,
+      mediaType: "application/pdf",
+      uri: "blob:x",
+      createdAt: "x",
+      updatedAt: "x",
+    }).uri).toBeUndefined();
+  });
+
   it("ignores malformed JSON without throwing", () => {
     const warn = vi.spyOn(console, "warn").mockImplementation(() => {});
     const storage = memoryStorage();