[Bug] Devcontainer default Python/PATH points outside the pinned Manim runtime

[alonshoa]

Summary

The devcontainer image contains the expected pinned Manim runtime under /opt/venv, but the default command environment resolves python to /usr/local/bin/python. That interpreter does not have the project runtime dependencies installed, so the documented/default post-create style command fails unless /opt/venv/bin/python and /opt/venv/bin are used explicitly.

Observed behavior

Running the doctor flow with the default python inside the built devcontainer fails:

python -m pip install --no-deps -e .
python -m manim_studio.cli doctor --catalog

Observed failures include:

• ModuleNotFoundError: No module named 'yaml'
• Python import: manim: No module named 'manim'
• Python import: manim_slides: No module named 'manim_slides'
• Manim CLI: manim was not found on PATH
• Manim Slides CLI: manim-slides was not found on PATH

Expected behavior

The devcontainer default shell and post-create command should use the pinned runtime where Manim Studio dependencies are available, so this should pass without manually specifying /opt/venv/bin/python or patching PATH per command.

Verification

The same checks pass when run with the pinned venv explicitly:

PATH=/opt/venv/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin \
  /opt/venv/bin/python -m manim_studio.cli doctor --catalog

With that environment:

• Manim 0.20.1: OK
• manim-slides 5.6.0: OK
• FFmpeg, LaTeX, XeLaTeX, dvisvgm, Hebrew font: OK
• strict catalog validation: OK, 5 scenes
• python -m unittest discover -s tests -v: OK, 64 tests
• real review renders for examples/square_to_circle and examples/basic_slide: OK, smoke render and contact sheet generated
• real final render for examples/square_to_circle: OK
• real build examples --profile review: OK

Likely fix

Update .devcontainer/Dockerfile and/or .devcontainer/devcontainer.json so the default environment prepends /opt/venv/bin to PATH, and set VS Code / post-create commands to use /opt/venv/bin/python or a shell where python resolves to the venv interpreter.

Also note: pytest is not installed in the devcontainer. CI uses python -m unittest discover -s tests -v, which currently passes.