[docs, examples, deps] chore: refresh benchmarks and public recipes

[yyDing1]

Summary

• Refresh inference and RL benchmark results and documentation.
• Document Harbor as a supported task format and clarify Agent configurations.
• Update the Claude Code RL recipe and remove the legacy black-box recipe.
• Exclude internal Seed Sandbox tests from public CI.
• Bump the verl submodule to the latest upstream main.

Testing

• MkDocs strict build passed.
• 167 verl integration tests passed.
• 30 sandbox unit tests passed.

[codecov-commenter]

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Codecov Report

✅ All modified and coverable lines are covered by tests.

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