feat(action): add Markdown to HTML publishing workflow

- Introduce a GitHub Action to convert Markdown files to HTML using Pandoc
- Configure steps for repository checkout, git setup, and branch management
- Include scripts for Markdown conversion, Pandoc installation, and git setup
- Automate the publishing of HTML output to a specified branch

action.yml

@@ -0,0 +1,85 @@
+name: "Markdown → HTML Publisher"
+description: >
+  Converts all *.md files in the given path (recursively) to HTML via Pandoc
+  and commits the result into the specified branch as an orphan branch,
+  replacing the entire branch content and removing history.
+
+inputs:
+  path:
+    description: "Directory to scan for Markdown files (default: $GITHUB_WORKSPACE)"
+    required: false
+  branch:
+    description: "Target branch that will receive the generated HTML"
+    required: false
+    default: pages
+
+runs:
+  using: composite
+  steps:
+    # 0) Checkout repository with full history so we can delete/reset branches
+    - name: Checkout repository
+      uses: actions/checkout@v4
+      with:
+        fetch-depth: 0
+
+    # 1) Configure git author (uses default values if none supplied)
+    - name: Setup git author
+      shell: bash
+      run: |
+        bash "${{ github.action_path }}/scripts/setup-git.sh"
+
+    # 2) Install or ensure pandoc is present
+    - name: Install pandoc
+      shell: bash
+      run: |
+        bash "${{ github.action_path }}/scripts/install-pandoc.sh"
+
+    # 3) Convert Markdown files to HTML into a temporary directory
+    - name: Convert Markdown tree
+      shell: bash
+      run: |
+        SRC_DIR="${{ inputs.path }}"
+        [[ -z "$SRC_DIR" ]] && SRC_DIR="$GITHUB_WORKSPACE"
+        TMP_DIR="$(mktemp -d)"
+        bash "${{ github.action_path }}/scripts/convert-md-tree.sh" "$SRC_DIR" "$TMP_DIR"
+        echo "TMP_DIR=$TMP_DIR" >> "$GITHUB_ENV"
+
+    # 4) Delete target branch (if it exists) and create new orphan branch
+    - name: Recreate orphan target branch
+      shell: bash
+      run: |
+        TARGET_BRANCH="${{ inputs.branch }}"
+        [[ -z "$TARGET_BRANCH" ]] && TARGET_BRANCH="pages"
+
+        if git show-ref --quiet "refs/heads/$TARGET_BRANCH"; then
+          git branch -D "$TARGET_BRANCH"
+        fi
+
+        git switch --orphan "$TARGET_BRANCH"
+        git rm -rf . || true
+
+        echo "TARGET_BRANCH=$TARGET_BRANCH" >> "$GITHUB_ENV"
+
+    # 5) Replace contents of the branch with generated HTML
+    - name: Replace branch contents
+      shell: bash
+      run: |
+        shopt -s dotglob
+        rm -rf ./* || true
+        cp -r "$TMP_DIR"/. .
+        rm -rf "$TMP_DIR"
+
+    # 6) Commit and push changes if there are any
+    - name: Commit and push changes
+      shell: bash
+      run: |
+        TARGET_BRANCH="${TARGET_BRANCH:-${{ inputs.branch }}}"
+        [[ -z "$TARGET_BRANCH" ]] && TARGET_BRANCH="pages"
+        if git status --porcelain | grep -q .
+        then
+          git add .
+          git commit -m "Automatic HTML publish: $(date -u +'%Y-%m-%d %H:%M:%S UTC')"
+          git push --force origin "$TARGET_BRANCH"
+        else
+          echo "ℹ️  No changes to commit."
+        fi