feat(agent): autonomy-levels framework (observe→…→auto)

[JSONbored]

Parent epic: #768 (Phase 0).

Goal

A first-class autonomy level per repo, per action class: observe → suggest → propose → auto+approval → auto. The dial everything else reads before acting.

Deliverables

• Autonomy-level enum + per-action-class type (review/merge/close/label/...)
• Persisted on repositorySettings (DB) + resolvable via the yml>DB>defaults resolver
• A single resolveAutonomy(repo, actionClass) gate that the action layer (N6) consults
• Deny-by-default for every action class

Context

src/services/control-panel-roles.ts, repositorySettings schema (src/api/routes.ts ~537), focus-manifest resolver.

Milestone: M2.