* feat(agents): create agent registry and service
* fix: mark agent offline only if the session was removed properly
* refactor: centralize agent backup lifecycle state
* refactor: simplify session management
* refactor: move effect / async boundary in one place
* chore: regen migration
* refactor: improve error handling
* chore: pr feedback
* feat(runtime): start and ship the local agent
* refactor: gate local agent behind feature flag
* chore: skip agent manager if flag is false
* fix: hot reload agents
* test: fix config tests
