Add Claude Agents integration

[adagradschool]

Summary

• add a new promptlayer.integrations.claude_agents integration with get_claude_config() and typed config objects
• vendor the PromptLayer Claude plugin into the package and add a maintainer vendoring script plus Make target
• add packaging/test coverage for the optional claude-agents extra and vendored asset resolution

Verification

• Unit Tests
• installed-wheel smoke import of get_claude_config()
• Verified E2E locally