feat: add agentId filter to aggregation queries

[jpleva91]

Context

packages/storage/src/aggregation-queries.ts has team-level aggregation but no way to filter by agent. The sessions table now has an indexed agent_id column (migration v5).

Work Items

1. Add agentId?: string to AggregationTimeFilter interface
2. Wire it into buildTimeConditions() to join/filter against sessions.agent_id
3. Refactor agentSummaries() to use indexed sessions.agent_id instead of json_extract() on RunStarted event data — much faster for large datasets
4. Update tests

Files

• packages/storage/src/aggregation-queries.ts
• packages/storage/src/types.ts (AggregationTimeFilter)
• packages/storage/tests/