fix(offline): stop offline white-screen and replay paused structural mutations

Fixes the offline-sync defects QA found on PR #120 (#237/#238/#220).

Blank-shell / white-screen on offline reload (HIGH):
- auth-query.tsx: the useCollabToken retry predicate read
  `error.response.status` unguarded. Offline the collab-token POST rejects as
  an axios NETWORK error (isAxiosError true, response undefined), so `.status`
  threw an uncaught TypeError in the React Query retryer BEFORE React mounted,
  white-screening every route. Extracted the predicate as `collabTokenRetry`
  and guarded it with optional chaining (`error.response?.status === 404`).
- user-provider.tsx: gated the whole <Layout> on useCurrentUser() and returned
  a bare `<></>` on any error, blanking every authenticated route offline even
  when cached data existed. Now renders the cached app when a (stale) user is
  present and an explicit OfflineFallback when there is no user to fall back on.
- query-persister.ts / make-offline.ts: persist and warm the ['currentUser']
  query so the auth gate can hydrate offline (pinned pages now survive relaunch).

Offline structural create/move/comment silently lost on reload (HIGH):
- offline-mutations.ts: register setMutationDefaults (default mutationFns) for
  stable mutation keys and tag useCreatePageMutation / useMovePageMutation /
  useCreateCommentMutation with those keys. A paused mutation dehydrated to
  IndexedDB while offline now has a mutationFn after reload, so
  resumePausedMutations() replays it on reconnect instead of no-op'ing.

Tests (client vitest): collabTokenRetry no longer throws on a no-response
network error; UserProvider renders cached children / the offline fallback (not
a blank fragment) on a network error; a rehydrated paused create/move is
replayable via resumePausedMutations; currentUser persist-root coverage.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/client/src/features/auth/queries/auth-query.test.ts

@@ -0,0 +1,43 @@
+import { describe, it, expect } from "vitest";
+import { AxiosError } from "axios";
+import { collabTokenRetry } from "./auth-query";
+
+// Regression for the offline white-screen (#237/#238): offline the collab-token
+// POST rejects as an axios NETWORK error (isAxiosError === true but
+// error.response === undefined). The old predicate read `error.response.status`
+// without a guard and threw an uncaught TypeError inside the React Query retryer
+// BEFORE React mounted, blanking the whole app. The predicate must stay total.
+describe("collabTokenRetry", () => {
+  it("does NOT throw and returns a retryable value for a network error with no response (offline)", () => {
+    // An axios error with no `response` is exactly the offline/network-failure shape.
+    const networkError = new AxiosError("Network Error");
+    expect(networkError.response).toBeUndefined();
+
+    let result: boolean | number = false;
+    expect(() => {
+      result = collabTokenRetry(0, networkError);
+    }).not.toThrow();
+    // Network failures stay retryable (truthy), matching the original intent.
+    expect(result).toBe(true);
+  });
+
+  it("returns false (no retry) for a real 404 response", () => {
+    const notFound = new AxiosError("Not Found");
+    notFound.response = { status: 404 } as AxiosError["response"];
+    expect(collabTokenRetry(0, notFound)).toBe(false);
+  });
+
+  it("retries for a non-404 response (e.g. 500)", () => {
+    const serverError = new AxiosError("Server Error");
+    serverError.response = { status: 500 } as AxiosError["response"];
+    expect(collabTokenRetry(0, serverError)).toBe(true);
+  });
+
+  it("does not throw and retries for a non-axios error", () => {
+    let result: boolean | number = false;
+    expect(() => {
+      result = collabTokenRetry(0, new Error("boom"));
+    }).not.toThrow();
+    expect(result).toBe(true);
+  });
+});

apps/client/src/features/auth/queries/auth-query.tsx

@@ -3,6 +3,27 @@ import { getCollabToken, verifyUserToken } from "../services/auth-service";
 import { ICollabToken, IVerifyUserToken } from "../types/auth.types";
 import { isAxiosError } from "axios";
 
+/**
+ * Retry predicate for the collab-token query.
+ *
+ * Offline (or any network failure) the POST rejects as an axios NETWORK error:
+ * `isAxiosError(error) === true` but `error.response === undefined`. Reading
+ * `error.response.status` without a guard threw an uncaught TypeError inside the
+ * React Query retryer BEFORE React mounted, white-screening the whole app on an
+ * offline cold boot (#237/#238). Optional-chaining `error.response?.status`
+ * keeps the predicate total: a network error (no response) is retryable, a real
+ * 404 is not. Extracted (and exported) so it can be unit-tested in isolation.
+ */
+export function collabTokenRetry(
+  _failureCount: number,
+  error: Error,
+): boolean {
+  if (isAxiosError(error) && error.response?.status === 404) {
+    return false;
+  }
+  return true;
+}
+
 export function useVerifyUserTokenQuery(
   verify: IVerifyUserToken,
 ): UseQueryResult<any, Error> {
@@ -22,13 +43,7 @@ export function useCollabToken(): UseQueryResult<ICollabToken, Error> {
     //refetchInterval: 12 * 60 * 60 * 1000, // 12hrs
     //refetchIntervalInBackground: true,
     refetchOnMount: true,
-    //@ts-ignore
-    retry: (failureCount, error) => {
-      if (isAxiosError(error) && error.response.status === 404) {
-        return false;
-      }
-      return 10;
-    },
+    retry: collabTokenRetry,
     retryDelay: (retryAttempt) => {
       // Exponential backoff: 5s, 10s, 20s, etc.
       return 5000 * Math.pow(2, retryAttempt - 1);