Persist App Core runtime history

[hhuumm]

Summary

• persist App Core sessions and timestamped stdout, stderr, and system events in each project's SQLite database
• hydrate the latest runtime output after CodePilot restarts and finalize sessions on stop, exit, errors, and desktop shutdown
• retain up to 100 sessions and 20,000 events per project while rendering the latest 500 in App Core
• mark App Core output as persisted locally and document the local-log privacy boundary

Verification

• npm run check (54 tests)
• npm --prefix desktop run typecheck
• npm run desktop:build