Fix documentation deployment (switch to HTTPS via GITHUB_TOKEN)

[Cardoza2]

Summary

• Removes DOCUMENTER_KEY from the workflow env — its presence caused Documenter to use the SSH code path, which failed with git@github.com: Permission denied (publickey) since no valid deploy key was configured
• Adds if: github.event_name != 'pull_request' guard so deployment is skipped on PRs (docs still build to catch errors)
• Updates actions/checkout@v2 → @v4 and julia-actions/setup-julia@v1 → @v2
• Moves PYTHON: "" into the build step (needed since make.jl calls Plots.pyplot())
• Adds comments explaining the auth strategy so future maintainers know no additional secrets need to be configured

Test plan

• Merge to master and confirm the Documentation workflow completes without the git fetch upstream SSH error
• Confirm gh-pages branch is updated and docs appear at the expected URL
• Open a test PR and confirm the build step runs but the deploy step is skipped

🤖 Generated with Claude Code

[Copilot]

Pull request overview

Fixes the GitHub Actions documentation deployment path by switching Documenter to use GITHUB_TOKEN (HTTPS) rather than the SSH deploy-key path, and updates workflow dependencies accordingly.

Changes:

• Update docs workflow to use actions/checkout@v4 and julia-actions/setup-julia@v2.
• Remove DOCUMENTER_KEY from the docs deploy environment and rely on GITHUB_TOKEN.
• Add ignore rules for docs build artifacts and Claude-related local files.

Reviewed changes

Copilot reviewed 1 out of 2 changed files in this pull request and generated 2 comments.

File	Description
.gitignore	Ignores docs/build/ and Claude-related local artifacts.
.github/workflows/Documentation.yml	Switches docs deployment auth strategy to HTTPS via GITHUB_TOKEN and updates action versions.

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[Copilot]

Because this workflow runs on pull_request and the job requests contents: write, a PR from a branch in the same repo would execute untrusted code with a write-capable GITHUB_TOKEN. Consider restructuring into two jobs: a PR-safe build job with read-only permissions, and a deploy job (push/tag only) that has contents: write and pushes to gh-pages. This also aligns with separating build vs deploy logic.