feat(cli): add account members command

[thebiglabasky]

Summary

• add checkly account members as a read-only command backed by /v1/accounts/me/members
• render account members and invites in table/markdown, with raw JSON output preserved
• document the command in the embedded Checkly skill context and regenerate the public skill output

Validation

• npx vitest --run src/formatters/__tests__/account-members.spec.ts src/commands/__tests__/command-metadata.spec.ts
• npm run lint
• npm run prepare:ai-context --workspace packages/cli && npm run prepare:ai-context

Note: npm run prepare:dist --workspace packages/cli was attempted earlier and is currently blocked by existing lru-cache declaration errors under node_modules.