- Added per-session retain queues with size/time auto-flush, recursive drain, and lifecycle flushes on end/clear/enqueue.
- Changed `hindsight-retain` to validate session state, enqueue writes, and return `Memory queued.` immediately.
- Added `notice` event support and handlers that route error/warning/status messages with source-aware formatting.
- Updated client and tests with shared request mapping, `RequestOptions`, `buildMemoryItem`, and expanded batch/list/doc APIs.