Feature: Persist Project Chat Sessions and Messages with ElectricSQL + TanStackDB #49

Description

Persist chat sessions and messages for project-scoped chat using ElectricSQL + TanStackDB. Sessions must be scoped by both workspace_id and project_id, with live sync behavior in the client.

Acceptance Criteria

• Chat sessions persist with workspace_id and project_id associations.
• Chat messages persist and reload correctly on refresh.
• Assistant responses stream and reconcile into persisted message content.
• Live updates sync via Electric shapes/TanStackDB collections.
• Session titles are auto-generated (from first message heuristic) and stored.

Tasks

• Add/confirm DB schema for chat_sessions and chat_messages.
• Add Electric shapes for session/message tables.
• Add TanStackDB collections and queries for sessions/messages.
• Persist user message on send and assistant message on stream completion/reconciliation.
• Ensure project-scoped session querying is enforced in data access layer.
• Add tests for persistence + sync behavior.
• Update docs with schema and data flow notes.

Tracer Bullet Reference

Validated by tracer bullets for project streaming + multi-session UX.

Additional Context

Workspace id is available via user.workspaceId in app context.