Expand agent client with lifecycle operations and capability management

[David-patrick-chuks]

Summary

Broaden the agent module to better represent the lifecycle of Lily agents and their capabilities.

Why this matters

A developer-facing SDK should support more than creation and basic updates. Richer lifecycle operations make the SDK more credible as the main integration surface for agent infrastructure.

Scope

• Identify missing lifecycle operations from backend support.
• Add capability-focused agent update flows where appropriate.
• Add methods for activation, deactivation, or similar lifecycle semantics if available.
• Keep method naming clear and versionable.

Acceptance Criteria

• Agent client includes additional lifecycle-oriented methods.
• Public request and response types are added.
• Tests cover new methods.
• Docs or examples reflect the expanded workflow.

Dependencies

• Depends on Align core domain models with Lily backend response envelopes #1