v0.6.0

Changelog

• deb7777: fix(cmd): rename --api-key to --api-secret on urlbox auth (@gdameneses)
• 80f430b: feat(api): add Client interface + Response types (@gdameneses)
• 46ee99b: test(api): add httptest scaffolding for client / retry tests (@gdameneses)
• 53d5fb7: feat(api): add retry with exponential backoff + Retry-After (@gdameneses)
• efc58af: test(api): white-box tests for parseRetryAfter + isRetryable + leak comment (@gdameneses)
• 0de0e0a: feat(api): add HTTPClient with auth, User-Agent, retry (@gdameneses)
• 38d2e69: fix: remove last stale --api-key breadcrumb + improve 409 hint (@gdameneses)
• 044042a: fix(doctor): hit /v1/user/me for auth check (Phase 1 bug) (@gdameneses)
• 0cc26b1: Merge branch 'feature/phase-4-render' into main (@gdameneses)