Add task attachment management to Self-Serve Studio. Extend graph, path outcomes, and flow logic. Update E2E/unit tests with attachment creation, upload, download, deletion flows, and related validations.

tests/e2e/support/network.js

@@ -6108,6 +6108,7 @@ export async function mockApi(page, options = {}) {
         const key = `${body.lane}:${String(body.reg || "").toUpperCase()}:${body.question}:${body.value}`;
         const responseSummary = selfServe.answerResponseByKey[key] || null;
 
+        await maybeDelayFixtureResponse(selfServe.answerResponseDelayMs);
         await route.fulfill(
           json({
             data: {
@@ -6908,7 +6909,7 @@ export async function primeMockSession(page, { token = "e2e-token", bootPath = "
       (response) => {
         return response.request().method() === "GET" && response.url().includes("/auth/session");
       },
-      { timeout: 10_000 }
+      { timeout: 30_000 }
     )
     .catch(() => null);
   await page.goto(bootPath, { waitUntil: "domcontentloaded" });