rivals-api 5.2.0

• Expose partial_result for overall summaries when only some requested modes
  have data, while retaining null full-scope fields and explicit missing modes.
  Add regression tests ensuring failures in each provider preserve usable
  overall/hero/class summaries from the other providers.
• Add bounded random delay above the configured request interval to reduce
  regular request bursts. Explicit request spacing remains a minimum; provider
  cooldowns are still respected by HTTP and browser requests.

Validation: 220 tests passed; Ruff passed; wheel/source archive built and inspected.