ci: Add GitHub Pages documentation workflow

[raifdmueller]

Summary

Adds automated documentation build and deployment via GitHub Actions using docToolchain.

Changes

• Add .github/workflows/gh-pages.yml workflow
• Add build/ to .gitignore

Workflow Features

• Build: Runs on every PR and push to main
• Deploy: Only deploys to GitHub Pages on push to main
• Uses docToolchain generateSite to build arc42 documentation
• Uses modern GitHub Pages deployment (actions/deploy-pages@v4)
• Requires Java 17 (Temurin distribution)

Prerequisites

After merging, enable GitHub Pages in repository settings:

1. Go to Settings > Pages
2. Source: "GitHub Actions"

Tested Locally

$ ./dtcw generateSite
BUILD SUCCESSFUL in 1m 32s
3 actionable tasks: 3 executed

Test plan

• Build works locally with ./dtcw generateSite
• Output generated in build/microsite/output/
• GitHub Actions workflow runs successfully
• Documentation accessible via GitHub Pages URL

Closes #24

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR adds automated documentation building and deployment using GitHub Actions and docToolchain. The workflow builds arc42 documentation on every PR and push to main, but only deploys to GitHub Pages when changes are pushed to the main branch.

Changes:

• Adds GitHub Actions workflow for building and deploying documentation via GitHub Pages
• Excludes build/ directory from version control

Reviewed changes

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

File	Description
.gitignore	Adds build/ directory to ignore list for docToolchain build output
.github/workflows/gh-pages.yml	Implements automated documentation build/deploy workflow with Java 17 and docToolchain

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