fix: serialize prettier formatting to prevent flaky tests

[veksen]

Summary

• prettier-plugin-sql is not safe to call concurrently. QueryCache.sync() runs up to 10 RecentQuery.analyze() calls in parallel, each calling prettier.format(). Under CI load, some calls throw silently (caught by the existing try/catch), causing queries to retain their original lowercase casing instead of being uppercased — leading to non-deterministic test failures.
• Adds a mutex (Sema(1)) around formatQuery to serialize prettier calls, making output deterministic.

Test plan

• All 153 tests pass locally
• Specifically verified remote.test.ts (8 tests) and query-optimizer.test.ts (5 tests) — both previously failing in the release CI job

🤖 Generated with Claude Code

[github-actions]

Query Doctor Analysis

View full run details

82 queries analyzed

2 pre-existing issues

• SELECT "guests"."id", "guests"."session_id", "guests"."username", "guests"."avatar_path", "guests"."color", "guests"."side", "guests"."audio_recording_path", "guests"."audio_recording_public", "gue...
  index assets(event_id, uploader_id, inserted_at desc)
  cost 15,918 → 1,631 (90% reduction)
• SELECT * FROM guest_ip_addresses WHERE ip_address = '127.0.0.1';
  index guest_ip_addresses(ip_address)
  cost 126 → 9 (93% reduction)

_{Using assumed statistics (10000 rows/table). For better results, sync production stats.}