feat: add Execute reference clients

[abrichr]

Summary

• add bearer-token metadata to the generated public Execute v1 OpenAPI document
• add a small standard-library Python client and dependency-free Python/TypeScript reference clients
• keep Cloud implementation, partner provisioning, application packs, evidence bytes, and webhooks private

Contract

• preserves released Execute v1 schemas, the body idempotency key, and the v1 resource paths
• uses a configurable base URL; the Cloud reference base is https://app.openadapt.ai/api

Checks

• full package test suite: 257 passed
• focused lint and source-boundary checks pass

Draft until the proprietary Cloud implementation aligns exactly to the released v1 public contract and durable signed webhooks land.