Greptile Summary

This PR adds support for specifying agents.*.sandbox.docker.setupCommand as either a string or an array of strings, normalizing arrays by joining with newlines to create valid multi-command shell scripts.

The implementation is clean and correct:

• Zod schema properly accepts both string and string array inputs
• Array normalization transforms arrays to newline-delimited strings that work with sh -lc execution
• Test validates the core functionality with a realistic multi-step setup example
• CHANGELOG accurately documents the fix
• Type documentation updated to reflect array support

The change maintains backward compatibility (strings still work) and properly addresses issue #31932 where array entries were concatenating without separators.

Confidence Score: 5/5

• This PR is safe to merge with minimal risk
• Simple, well-tested change that adds optional array support to existing string field with proper normalization. Maintains backward compatibility and includes regression test coverage.
• No files require special attention

_{Last reviewed commit: 30dc547}

Landed via temp rebase onto main.

• Gate: bunx vitest run src/config/config.sandbox-docker.test.ts
• Land commit: 32e4558
• Merge commit: 9b8e642

Thanks @liuxiaopai-ai!