fix(devcontainers): build with Python 3.13 while dependencies are unavailable

[gforsyth]

We bumped the default devcontainer Python version to 3.14 in rapidsai/devcontainers#677 but some repos (like cuml) have optional dependencies without Python 3.14 support.

We need to override the Python version temporarily until those deps catch up.

I'll also open a tracking issue so we remember to undo this.

[coderabbitai]

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📥 Commits

Reviewing files that changed from the base of the PR and between b027fff and 19d8a1f.

📒 Files selected for processing (4)

• .devcontainer/cuda12.9-conda/devcontainer.json
• .devcontainer/cuda12.9-pip/devcontainer.json
• .devcontainer/cuda13.1-conda/devcontainer.json
• .devcontainer/cuda13.1-pip/devcontainer.json

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📝 Walkthrough

Summary by CodeRabbit

• Chores
  • Standardized Python version to 3.13 across all development container configurations.

Walkthrough

Added containerEnv configuration entries to four devcontainer JSON files, explicitly setting the PYTHON_VERSION environment variable to 3.13 across CUDA 12.9 and 13.1 conda and pip-based development containers.

Changes

Cohort / File(s)	Summary
Devcontainer Python Version Override .devcontainer/cuda12.9-conda/devcontainer.json, .devcontainer/cuda12.9-pip/devcontainer.json, .devcontainer/cuda13.1-conda/devcontainer.json, .devcontainer/cuda13.1-pip/devcontainer.json	Added containerEnv property setting PYTHON_VERSION to 3.13 in all four devcontainer configurations. The pip-based variants include a TODO comment noting this is a temporary override pending Python 3.14 dependency support.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change: adding Python 3.13 configuration to devcontainers as a temporary fix for dependency compatibility issues.
Description check	✅ Passed	The description clearly explains the context (Python 3.14 bump), the problem (missing dependency support), and the solution (temporary Python 3.13 override).
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

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[bdice]

JavaScript comments technically aren't valid in JSON files but sometimes parsers are relaxed and won't complain...

[gforsyth]

Who needs comments? (Everyone).

I had forgotten this -- hopefully devcontainer parsing is more relaxed

[bdice]

This actually did come back to bite me. :( I do some parsing of the devcontainer files with jq and this broke it. I'm working around it with a sed command to remove comments in my tooling... but we should probably remove it.

[gforsyth]

/merge