Add retry mechanism for thread listing failures in syncThreads (#1931)

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## Description

Please provide a clear description of your changes.

---

## Type of Change

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- [ ] 🐛 Bug fix (non-breaking change which fixes an issue)
- [ ] ✨ New feature (non-breaking change which adds functionality)
- [ ] 💥 Breaking change (fix or feature with breaking changes)
- [ ] 📝 Documentation update
- [ ] 🎨 UI/UX improvement
- [ ] 🔒 Security enhancement
- [ ] ⚡ Performance improvement

## Areas Affected

Please check all that apply:

- [ ] Email Integration (Gmail, IMAP, etc.)
- [ ] User Interface/Experience
- [ ] Authentication/Authorization
- [ ] Data Storage/Management
- [ ] API Endpoints
- [ ] Documentation
- [ ] Testing Infrastructure
- [ ] Development Workflow
- [ ] Deployment/Infrastructure

## Testing Done

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- [ ] Unit tests added/updated
- [ ] Integration tests added/updated
- [ ] Manual testing performed
- [ ] Cross-browser testing (if UI changes)
- [ ] Mobile responsiveness verified (if UI changes)

## Security Considerations

For changes involving data or authentication:

- [ ] No sensitive data is exposed
- [ ] Authentication checks are in place
- [ ] Input validation is implemented
- [ ] Rate limiting is considered (if applicable)

## Checklist

- [ ] I have read the [CONTRIBUTING](https://github.com/Mail-0/Zero/blob/staging/.github/CONTRIBUTING.md) document
- [ ] My code follows the project's style guidelines
- [ ] I have performed a self-review of my code
- [ ] I have commented my code, particularly in complex areas
- [ ] I have updated the documentation
- [ ] My changes generate no new warnings
- [ ] I have added tests that prove my fix/feature works
- [ ] All tests pass locally
- [ ] Any dependent changes are merged and published

## Additional Notes

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---

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<!-- This is an auto-generated description by cubic. -->
---

## Summary by cubic
Added a retry mechanism to syncThreads so that if thread listing fails, it waits 1 minute and retries the same page instead of skipping it.

- **Bug Fixes**
  - Prevents data loss by ensuring failed thread listing pages are retried, not skipped.

<!-- End of auto-generated description by cubic. -->



<!-- This is an auto-generated comment: release notes by coderabbit.ai -->

## Summary by CodeRabbit

* **Bug Fixes**
  * Improved error handling and retry logic to prevent immediate failures when listing threads, enabling automatic retries after a short delay.
  * Enhanced logging to provide clearer information about retry attempts and page processing status.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

Author: MrgSub

apps/server/src/routes/agent/index.ts

@@ -1214,35 +1214,45 @@ export class ZeroDriver extends DurableObject<ZeroEnv> {
               }),
             ),
             Effect.catchAll((error) => {
-              console.error(`[syncThreads] Failed to list threads for folder ${folder}:`, error);
-              return Effect.fail(
-                new ThreadListError(`Failed to list threads for folder ${folder}`, error),
+              console.error(`[syncThreads] Failed to list threads for folder ${folder}, retrying in 1 minute:`, error);
+              return Effect.sleep('1 minute').pipe(
+                Effect.tap(() => Effect.sync(() => 
+                  console.log(`[syncThreads] Retrying page ${result.pagesProcessed} for folder ${folder}`)
+                )),
+                Effect.andThen(() => Effect.succeed({ threads: [], nextPageToken: pageToken }))
               );
             }),
           );
 
-          // Process threads with controlled concurrency to avoid rate limits
-          const threadIds = listResult.threads.map((thread) => thread.id);
-          const syncEffects = threadIds.map(syncSingleThread);
+          // Only process threads if we actually got some (not a retry with empty result)
+          if (listResult.threads.length > 0) {
+            // Process threads with controlled concurrency to avoid rate limits
+            const threadIds = listResult.threads.map((thread) => thread.id);
+            const syncEffects = threadIds.map(syncSingleThread);
 
-          yield* Effect.all(syncEffects, { concurrency: 1, discard: true }).pipe(
-            Effect.tap(() =>
-              Effect.sync(() =>
-                console.log(`[syncThreads] Completed page ${result.pagesProcessed}`),
+            yield* Effect.all(syncEffects, { concurrency: 1, discard: true }).pipe(
+              Effect.tap(() =>
+                Effect.sync(() =>
+                  console.log(`[syncThreads] Completed page ${result.pagesProcessed}`),
+                ),
               ),
-            ),
-            Effect.catchAll((error) => {
-              console.error(
-                `[syncThreads] Failed to process threads on page ${result.pagesProcessed}:`,
-                error,
-              );
-              return Effect.succeed(undefined);
-            }),
-          );
+              Effect.catchAll((error) => {
+                console.error(
+                  `[syncThreads] Failed to process threads on page ${result.pagesProcessed}:`,
+                  error,
+                );
+                return Effect.succeed(undefined);
+              }),
+            );
 
-          result.synced += listResult.threads.length;
-          pageToken = listResult.nextPageToken;
-          hasMore = pageToken !== null && shouldLoop;
+            result.synced += listResult.threads.length;
+            pageToken = listResult.nextPageToken;
+            hasMore = pageToken !== null && shouldLoop;
+          } else {
+            // This was a retry, don't update pageToken or hasMore - retry the same page
+            console.log(`[syncThreads] Retrying same page ${result.pagesProcessed} after error`);
+            result.pagesProcessed--; // Don't count failed pages
+          }
 
           // Send state update after first page is processed to give accurate feedback
           if (!firstPageProcessed) {