fix(chat): make drawer refresh lightweight and monotonic

[hamzamerzic]

Summary

• project chat-list metadata in SQL instead of hydrating full transcripts
• cancel competing list reads and remove redundant refresh work
• make create-chat reconciliation monotonic so stale service-worker responses cannot hide or downgrade the new chat

Validation

• drawer race and stale-response regressions
• backend chat-list regressions
• full frontend unit/build and backend pre-push suites

[hamzamerzic]

Superseded by #108 after this focused drawer head completed all checks green but became behind required-up-to-date main. The same reviewed commits passed fresh aggregate CI and merged as 5baaf65.