feat: support overriding Docker image entrypoint

[Yunnglin]

Summary

• add an optional entrypoint field to DockerSandboxConfig
• pass explicit overrides through to Docker, including [] to clear an image entrypoint
• preserve existing inheritance when the field is unset

Validation

• pytest -q tests/test_sandbox.py::TestSandboxBasicFunctionality::test_docker_entrypoint_override tests/test_sandbox.py::TestSandboxBasicFunctionality::test_docker_entrypoint_inherits_image_by_default
• pre-commit run --files ms_enclave/sandbox/model/config.py ms_enclave/sandbox/boxes/docker_sandbox.py tests/test_sandbox.py

This is required for EvalScope to run the pinned OmniDocBench v1.6 image as a reusable sandbox pool without maintaining a derived image.

[gemini-code-assist]

Caution

The consumer version of Gemini Code Assist on GitHub has been sunset. All code review activity has officially ceased.

[Copilot]

🟢 Ready to approve

The changes cleanly implement the requested entrypoint override semantics and include targeted tests for both explicit override and default inheritance behavior.

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Pull request overview

This PR adds support for explicitly overriding a Docker image’s entrypoint via DockerSandboxConfig, including the ability to clear an image-defined entrypoint by passing an empty list, while preserving the existing “inherit from image” behavior when the field is unset.

Changes:

• Added optional entrypoint: Optional[Union[str, List[str]]] to DockerSandboxConfig.
• Updated DockerSandbox._create_container() to pass entrypoint through to docker-py only when explicitly set (including []).
• Added tests verifying JSON round-tripping for entrypoint, explicit override behavior, and default inheritance behavior.

File summaries

File	Description
tests/test_sandbox.py	Adds coverage for entrypoint override/clearing and default inheritance behavior.
ms_enclave/sandbox/model/config.py	Introduces the new entrypoint config field with documentation.
ms_enclave/sandbox/boxes/docker_sandbox.py	Conditionally forwards entrypoint to container creation when not None (supports []).

Review details

• Files reviewed: 3/3 changed files
• Comments generated: 0
• Review effort level: Lite

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