Update Cloud CLI and MCP skills for session authentication

[xav-db]

Summary

• rewrite helix-cli around WorkOS-session-only Cloud authentication, brokered query/shell execution, explicit target resolution, and one-time product credentials
• keep helix-mcp focused on the existing read-only Insights surface
• add helix-query-mcp for brokered reads and durably confirmed writes
• add helix-admin-mcp for database key and tenant administration with durable confirmations
• update skill manifests, examples, references, and agent metadata

Related implementation PRs:

• HelixDB/helix-hyperscale#265
• Move Helix Cloud CLI to WorkOS sessions helix-db#1025

Verification

• validated helix-cli with skill-creator quick_validate
• validated helix-mcp with skill-creator quick_validate
• validated helix-query-mcp with skill-creator quick_validate
• validated helix-admin-mcp with skill-creator quick_validate
• git diff --check
• gitleaks committed-range scan