## 1. Implementation
- [x] 1.1 Update `heartbeatProcessor.js` to handle all numeric overflow types (`int16`, `int32`, `int64`) with two's complement.
- [x] 1.2 Prevent purely data-related Postgres failures from throwing away individual fallbacks within `databaseManager.js`.
- [x] 1.3 Add `insertHeartbeatEventsErrors` to `databaseManager.js` to sink rejected records.
- [x] 1.4 Wire `_emitRejectedRecord` in `heartbeatProcessor.js` to directly write all completely unprocessable heartbeats into the `heartbeat_events_errors` DB.
- [x] 1.5 Update the `openspec` specs with these newly supported overflow & validation fallback states.