Migrate event store from SQLite StorageFile to ApexStore event stream

[ElioNeto]

Problem

The event store currently uses StorageFile backed by SQLite to persist domain events. This is the heaviest user of SQLite and the primary bottleneck for deprecating it.

Current architecture

• Events stored in SQLite via StorageFile in packages/teamcode/src/storage/
• Events are appended sequentially with event_id, aggregate_id, event_type, data, timestamp
• Queries include: "all events for aggregate", "events by type", "events since timestamp"

Proposal

Replace SQLite event storage with an ApexStore-based event stream:

1. Key pattern: event:{aggregate_type}:{aggregate_id}:{timestamp}:{event_id} -> { "type": "...", "data": {...} }
2. Append: Single PUT with sequential timestamp key
3. Query by aggregate: GET /keys?prefix=event:session:{sessionId}: — prefix scan
4. Query by type: Requires secondary index or prefix pattern event:type:{event_type}:
5. Since timestamp: GET /keys?lower=event:session:{sessionId}:{timestamp} — range scan lower bound
6. Global stream: GET /scan with cursor pagination for replay/projection

Migration strategy

1. Add ApexStoreEventStore in packages/teamcode/src/storage/apex-store/event-store.ts
2. Implement the same interface as StorageFile
3. Add a feature flag apexstore_events in config
4. Run both stores in parallel during migration
5. One-way sync from SQLite -> ApexStore for existing events
6. When confident, remove SQLite event store

Dependencies

• ApexStore paginated cursor scan (for replay)
• ApexStore composite key range query (for since-timestamp scans)
• ApexStore batch delete (for event cleanup/retention)