feat(workflow): add XeLaTeX, multi-document, and font support for presentations

[prudhomm]

Summary

Extends the generated GitHub Actions workflow to support Beamer presentations with XeLaTeX compilation and multiple document outputs.

Changes

config.py

• Added get_documents_config() method for multi-document project configuration
• Added get_workflow_config() method for workflow-specific settings (output_dir, fonts_dir, install_fonts)
• Updated sample configuration with new [documents] and [workflow] sections

repository_setup.py

• Extended init_repository() to accept new parameters: additional_documents, output_dir, fonts_dir, install_fonts
• Extended _create_workflow() to support:
  • XeLaTeX compilation for presentations/posters (latexmk_use_xelatex: true)
  • Output directory configuration (-outdir=build)
  • Font installation step for CI (copies fonts to ~/.local/share/fonts/)
  • Multiple document compilation (additional documents like posters)
• Extended _get_workflow_template() with:
  • -xelatex flag for self-hosted runners
  • Font installation step when configured
  • Separate compilation steps for additional documents
  • Updated artifact and release files to include all PDFs
• Extended _create_pyproject() to include new configuration sections

New Configuration Options

[tool.article-cli.documents]
main = "presentation.tex"
additional = ["poster.tex"]

[tool.article-cli.workflow]
output_dir = "build"
fonts_dir = "fonts"
install_fonts = true

Testing

• All 71 repository_setup tests pass
• 2 pre-existing test failures (unrelated - due to environment variables)

Closes #3