feat(ci): add PDF-only update workflow

Allows updating paper and guide PDFs without version bumps or site changes.

.github/workflows/tinytorch-update-pdfs.yml

@@ -0,0 +1,174 @@
+name: '🔥 TinyTorch · 📄 Update PDFs Only'
+
+# =============================================================================
+# PDF-Only Update Workflow
+# =============================================================================
+# Rebuilds and deploys PDFs without touching the website, version, or tags.
+# Use this when you only need to update the paper or guide PDF.
+# =============================================================================
+
+on:
+  workflow_dispatch:
+    inputs:
+      update_paper:
+        description: 'Update Research Paper PDF'
+        type: boolean
+        default: true
+      update_guide:
+        description: 'Update Course Guide PDF'
+        type: boolean
+        default: true
+
+permissions:
+  contents: write
+
+jobs:
+  build-paper:
+    name: '📑 Build Research Paper'
+    runs-on: ubuntu-latest
+    if: inputs.update_paper
+    steps:
+      - name: 📥 Checkout
+        uses: actions/checkout@v4
+        with:
+          ref: main
+
+      - name: 📑 Compile Paper with LuaLaTeX
+        uses: xu-cheng/latex-action@v3
+        with:
+          root_file: paper.tex
+          working_directory: tinytorch/paper
+          latexmk_use_lualatex: true
+
+      - name: 📤 Upload PDF Paper
+        uses: actions/upload-artifact@v4
+        with:
+          name: TinyTorch-Paper
+          path: tinytorch/paper/paper.pdf
+          retention-days: 7
+
+  build-guide:
+    name: '📚 Build Course Guide'
+    runs-on: ubuntu-latest
+    if: inputs.update_guide
+    steps:
+      - name: 📥 Checkout
+        uses: actions/checkout@v4
+        with:
+          ref: main
+
+      - name: 🐍 Setup Python
+        uses: actions/setup-python@v5
+        with:
+          python-version: '3.11'
+          cache: 'pip'
+          cache-dependency-path: 'tinytorch/site/requirements.txt'
+
+      - name: 🟢 Setup Node.js (for Mermaid)
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+
+      - name: 📦 Install Mermaid CLI
+        run: npm install -g @mermaid-js/mermaid-cli
+
+      - name: 📦 Install dependencies
+        working-directory: tinytorch
+        run: |
+          pip install --upgrade pip
+          pip install -r site/requirements.txt
+          pip install -e .
+
+      - name: 📚 Generate LaTeX
+        working-directory: tinytorch/site
+        run: |
+          jupyter-book build . --builder latex --config _config_pdf.yml --toc _toc_pdf.yml
+          python3 scripts/latex_postprocessor.py
+          cp _static/logos/fire-emoji.png _build/latex/
+          cp _static/logos/logo-mlsysbook.png _build/latex/
+          cp _static/images/tito.png _build/latex/
+
+      - name: 📚 Compile PDF with XeLaTeX
+        uses: xu-cheng/latex-action@v3
+        with:
+          root_file: tinytorch-course.tex
+          working_directory: tinytorch/site/_build/latex
+          latexmk_use_xelatex: true
+
+      - name: 📤 Upload PDF Guide
+        uses: actions/upload-artifact@v4
+        with:
+          name: TinyTorch-Guide
+          path: tinytorch/site/_build/latex/tinytorch-course.pdf
+          retention-days: 7
+
+  deploy-pdfs:
+    name: '🚀 Deploy PDFs to gh-pages'
+    runs-on: ubuntu-latest
+    needs: [build-paper, build-guide]
+    if: always() && (needs.build-paper.result == 'success' || needs.build-guide.result == 'success')
+    steps:
+      - name: 📥 Checkout gh-pages
+        uses: actions/checkout@v4
+        with:
+          ref: gh-pages
+          path: gh-pages
+
+      - name: 📥 Download Paper PDF
+        if: needs.build-paper.result == 'success'
+        uses: actions/download-artifact@v4
+        with:
+          name: TinyTorch-Paper
+          path: ./artifacts/paper
+
+      - name: 📥 Download Guide PDF
+        if: needs.build-guide.result == 'success'
+        uses: actions/download-artifact@v4
+        with:
+          name: TinyTorch-Guide
+          path: ./artifacts/guide
+
+      - name: 📁 Update PDFs in gh-pages
+        run: |
+          cd gh-pages
+          mkdir -p tinytorch/_static/downloads
+
+          if [ -f ../artifacts/paper/paper.pdf ]; then
+            cp ../artifacts/paper/paper.pdf tinytorch/_static/downloads/TinyTorch-Paper.pdf
+            echo "✅ Updated TinyTorch-Paper.pdf"
+          fi
+
+          if [ -f ../artifacts/guide/tinytorch-course.pdf ]; then
+            cp ../artifacts/guide/tinytorch-course.pdf tinytorch/_static/downloads/TinyTorch-Guide.pdf
+            echo "✅ Updated TinyTorch-Guide.pdf"
+          fi
+
+          echo ""
+          echo "📦 Downloads folder:"
+          ls -la tinytorch/_static/downloads/
+
+      - name: 🚀 Push to gh-pages
+        working-directory: gh-pages
+        run: |
+          git config user.name "github-actions[bot]"
+          git config user.email "github-actions[bot]@users.noreply.github.com"
+
+          git add tinytorch/_static/downloads/
+          git commit -m "📄 Update TinyTorch PDFs" || echo "No changes to commit"
+          git push origin gh-pages
+
+  summary:
+    name: '📊 Summary'
+    runs-on: ubuntu-latest
+    needs: [build-paper, build-guide, deploy-pdfs]
+    if: always()
+    steps:
+      - name: 📊 Generate Summary
+        run: |
+          echo "## 📄 TinyTorch PDF Update" >> $GITHUB_STEP_SUMMARY
+          echo "" >> $GITHUB_STEP_SUMMARY
+          echo "| PDF | Status |" >> $GITHUB_STEP_SUMMARY
+          echo "|-----|--------|" >> $GITHUB_STEP_SUMMARY
+          echo "| 📑 Research Paper | ${{ needs.build-paper.result }} |" >> $GITHUB_STEP_SUMMARY
+          echo "| 📚 Course Guide | ${{ needs.build-guide.result }} |" >> $GITHUB_STEP_SUMMARY
+          echo "| 🚀 Deploy | ${{ needs.deploy-pdfs.result }} |" >> $GITHUB_STEP_SUMMARY