feat(ops): add robot action catalog model and API

[05F3759DF]

Context

Axon Agent will expose a local allowlist of pre-registered robot-side operations scripts. Keystone needs a catalog model and API so operators can see which actions a robot supports before creating action requests.

Scope

• Store each robot's reported action catalog from Axon Agent.
• Preserve action metadata such as id, title, description, argument schema, timeout, approval requirement, and risk level.
• Expose APIs to list available actions for a robot and retrieve a single action definition.
• Track catalog freshness and handle stale or missing agent reports.
• Reject catalog entries that are malformed or unsafe to display.

Acceptance Criteria

• Keystone stores and updates a robot's reported action catalog.
• Operators or UI clients can query available actions for a robot.
• Stale or missing action catalogs are distinguishable from empty catalogs.
• Action definitions expose argument schemas without exposing local command paths unnecessarily.
• Tests cover catalog create/update, malformed entries, stale catalog handling, and query behavior.

Related

• feat(agent): add local action registry for pre-registered ops scripts axon#90