Worker shutdown already persists an active session checkpoint, but startup only armed the boredom timer. That left a restarted active session dormant until a DM or boredom wake arrived.
This change detects a saved main-session checkpoint after the worker is listening and immediately activates the runner with a system resume event. Resting sessions without a checkpoint keep the existing boredom behavior.
Includes a regression test proving startup makes one immediate model request with the prior context and resume marker.
Verified:
- focused restart-resume regression test
- @nano/runtime typecheck
- full npm test suite