📝 Add docstrings to test/challenge-orchestrator

Docstrings generation was requested by @cuteolaf.

* #11 (comment)

The following files were modified:

* `crates/challenge-orchestrator/src/backend.rs`
* `crates/challenge-orchestrator/src/docker.rs`
* `crates/challenge-orchestrator/src/evaluator.rs`
* `crates/challenge-orchestrator/src/health.rs`
* `crates/challenge-orchestrator/src/lib.rs`
* `crates/challenge-orchestrator/src/lifecycle.rs`

Author: coderabbitai[bot]