[eval] Python + CLI: list and pull registered eval scenarios

[thorrester]

Part of #380
Depends on: #383

What

Read path for registered eval scenarios — Python API and CLI.

• Server route: GET /opsml/api/eval/scenarios — filterable by space, name, version, uid
• Python: query registered scenarios via registry interface, returns list of EvalRegistryRecord
• CLI: opsml eval list [--space X] [--name Y] [--version Z]
• Pagination follows existing QueryPageRequest / QueryPageResponse cursor pattern