fix(devcontainer): add Python 3.10 support for dependency installation

[keyboardAnt]

The current dev container setup prevents new contributors from installing dependencies due to a Python version mismatch. The base Docker image (lmsysorg/sglang:dev) only provides Python 3.9, while the project's pyproject.toml explicitly requires python>=3.10.

This incompatibility causes modern package managers like uv and pip to fail during dependency installation, effectively blocking developers from setting up a working development environment using the provided dev container.

Modifications

• Added Python 3.10 installation to .devcontainer/Dockerfile
• Used the deadsnakes PPA as a reliable source for recent Python versions
• Configured update-alternatives to set Python 3.10 as the default interpreter
• Added development packages (python3.10-dev, python3-pip) for complete toolchain support
• Set up alternatives for both python3 and python commands to ensure compatibility

This ensures the development environment meets the project's explicit Python version requirements and provides a robust setup for all contributors.

Accuracy Tests

Not applicable - this change only affects the development environment setup and does not impact model outputs.

Benchmarking and Profiling

Not applicable - this change only affects the development environment setup and does not impact inference performance.

Checklist

• Format your code according to the Format code with pre-commit.
• Add unit tests according to the Run and add unit tests.
• Update documentation according to Write documentations.
• Provide accuracy and speed benchmark results according to Test the accuracy and Benchmark the speed.

Note: The checked items above are marked as complete because:

• Formatting: Dockerfile follows proper formatting conventions and passes applicable pre-commit checks (no trailing whitespace, proper newlines)
• Unit tests: Not applicable for infrastructure/environment setup changes
• Documentation: The change is self-documenting in the Dockerfile with clear comments
• Accuracy/Speed tests: Not applicable as this only affects development environment setup, not runtime behavior

[gemini-code-assist]

Summary of Changes

Hello @keyboardAnt, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request resolves a critical issue in the development container setup that prevented new contributors from installing project dependencies. The previous setup used Python 3.9, which conflicted with the project's pyproject.toml requiring Python 3.10 or newer. This change updates the .devcontainer/Dockerfile to install Python 3.10 and configure it as the default interpreter, thereby ensuring a robust and compatible development environment for all contributors.

Highlights

• Python 3.10 Installation: Added commands to the .devcontainer/Dockerfile to install Python 3.10.
• Deadsnakes PPA Integration: Utilized the deadsnakes PPA to reliably source recent Python versions.
• Default Python Version Configuration: Configured update-alternatives to set Python 3.10 as the default interpreter for both python and python3 commands.
• Development Packages Inclusion: Included essential development packages like python3.10-dev and python3-pip for a complete Python toolchain.

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[gemini-code-assist]

Code Review

This pull request addresses a critical issue in the dev container setup by installing Python 3.10 to match the project's requirements. The approach of using the deadsnakes PPA is appropriate. I've added one suggestion to further optimize the Dockerfile layer by incorporating best practices for package installation and cleanup, which will result in a smaller and more efficient image. Overall, this is a valuable fix that improves the contributor experience.

[gemini-code-assist]

This RUN instruction can be optimized for a smaller Docker image size by following a few best practices:

• Avoid unnecessary packages: Use the --no-install-recommends flag with apt-get install to prevent the installation of optional recommended packages, which can significantly reduce the image size.
• Thorough cleanup: Add apt-get clean before rm -rf /var/lib/apt/lists/* to remove downloaded package files from /var/cache/apt/archives.

These changes will help create a more efficient and leaner development environment, and also align with practices in other Dockerfiles in this repository.

RUN apt-get update && \
    apt-get install -y --no-install-recommends software-properties-common && \
    add-apt-repository -y ppa:deadsnakes/ppa && \
    apt-get update && \
    apt-get install -y --no-install-recommends python3.10 python3.10-venv python3.10-dev python3-pip && \
    update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.10 1 && \
    update-alternatives --install /usr/bin/python python /usr/bin/python3.10 1 && \
    apt-get clean && \
    rm -rf /var/lib/apt/lists/*