Add Docker docs and test-docker justfile target

[blink1073]

References

N/A

Description

Adds documentation for the pre-built Docker image and a test-docker justfile target that validates the image after building.

Changes

• Add Docker installation section to README.md with instructions for pulling and running the image, including a note to click the token URL to open JupyterLab
• Add .dockerignore to exclude .git, .venv, and cache files from Docker builds
• Add test-docker justfile target that runs docker-build then verifies the octave kernelspec is listed and the octave executable is available
• Update the docker-build CI job to use just test-docker after the Buildx build (with GHA layer caching preserved via load: true)
• Remove .python-version (Python version is managed by Poetry)

Backwards-incompatible changes

None

Testing

Ran just test-docker locally — both checks pass (kernelspec listed, octave --version succeeds).

AI usage

• AI was used to generate or assist with this code
• The human author has reviewed and understands all AI-generated contributions

Tools: Claude (claude-sonnet-4-6)

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.64%. Comparing base (234777e) to head (57971dc).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #306   +/-   ##
=======================================
  Coverage   91.64%   91.64%           
=======================================
  Files           6        6           
  Lines         431      431           
=======================================
  Hits          395      395           
  Misses         36       36           

Flag	Coverage Δ
linux	91.41% <ø> (ø)
windows	91.64% <ø> (ø)

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