Keep local database operations responsive during sync

[ComputelessComputer]

Remove the CloudSync reconciliation barrier from renderer SQL while preserving native synced-write serialization.

---

Note

Medium Risk
Changes serialization timing around CloudSync workspace projection and E2EE cutover; race windows could affect sync consistency if assumptions about suspend/reconcile ordering are wrong.

Overview
CloudSync workspace projection reconciliation no longer holds the synced_write_barrier write lock for the whole configure_cloudsync_token_with_projection_inner flow. Validation, workspace claim, and cloudsync_suspend run first; the write lock is taken only after suspend when a projection is present. It is released explicitly after commit_cloudsync_workspace_projection and before apply_cloudsync_config_fail_closed, so renderer SQL (execute, transactions, proxy) can proceed during the final CloudSync reconfigure/start instead of staying blocked for the entire E2EE and staging work.

Tests for reconciliation_barrier_blocks_renderer_writes now assert that all three renderer write entry points block while the write guard is held and succeed after it is dropped.

^{Reviewed by Cursor Bugbot for commit 11fa15c. Bugbot is set up for automated code reviews on this repo. Configure here.}

[netlify]

✅ Deploy Preview for old-char canceled.

Name	Link
🔨 Latest commit	11fa15c
🔍 Latest deploy log	https://app.netlify.com/projects/old-char/deploys/6a60707af0829c0008bfa7ef

[cursor]

Cursor Bugbot has reviewed your changes using default effort and found 1 potential issue.

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit 3b8cd3f. Configure here.}