Add LaTeX build log artifacts to PDF workflow

.github/workflows/README.md

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+# GitHub Actions Workflows
+
+## Build Book PDF
+
+The `build-book-pdf.yml` workflow automatically builds the LaTeX book manuscript into a PDF.
+
+### How it works
+
+1. **Triggers**: The workflow runs when:
+   - Changes are pushed to the `book` branch in the `book/` directory
+   - Pull requests target the `book` branch with changes in `book/` directory
+   - Manually triggered from the Actions tab
+
+2. **Build process**:
+   - Checks out the repository
+   - Uses the `xu-cheng/latex-action@v3` to compile the LaTeX document
+   - Runs `latexmk` which automatically handles multiple pdflatex passes for cross-references
+   - Compiles `book/main.tex` into `book/main.pdf`
+
+3. **Output**:
+   - The generated PDF is uploaded as a GitHub Actions artifact (90-day retention)
+   - LaTeX build logs are uploaded as artifacts (30-day retention) for debugging
+   - Each workflow run creates:
+     - `book-pdf` artifact: Contains `main.pdf` (only on successful build)
+     - `latex-build-logs` artifact: Contains `.log`, `.aux`, and other build files (always uploaded)
+
+### Accessing the PDF and build logs
+
+After a workflow run:
+
+1. Go to the **Actions** tab in the GitHub repository
+2. Click on the workflow run you're interested in
+3. Scroll down to the **Artifacts** section
+4. Download the artifacts:
+   - **book-pdf**: The compiled PDF (available only if build succeeded)
+   - **latex-build-logs**: LaTeX log files for debugging (always available)
+
+Both artifacts are .zip files that need to be extracted after download.
+
+### Manual triggering
+
+You can manually trigger a build:
+
+1. Go to **Actions** tab
+2. Select **Build Book PDF** workflow
+3. Click **Run workflow** button
+4. Select the `book` branch
+5. Click **Run workflow**
+
+### LaTeX packages
+
+The workflow uses a full TeX Live distribution that includes all required packages:
+- graphicx, epsfig (for figures)
+- amsmath (for mathematical notation)
+- hyperref (for hyperlinks and cross-references)
+- geometry (for page layout)
+- longtable, dcolumn (for tables)
+- bm (for bold math)
+- And many more standard packages
+
+### Troubleshooting
+
+If the build fails:
+
+1. **Download the build logs**: 
+   - Go to the Actions tab and find the failed workflow run
+   - Scroll to the **Artifacts** section
+   - Download the `latex-build-logs` artifact
+   - Extract the .zip file and open `main.log` to see detailed error messages
+
+2. **Check the workflow logs**:
+   - Click on the failed job in the Actions tab
+   - Review the "Compile LaTeX document" step for immediate error output
+
+3. **Common issues**:
+   - Missing figures: Ensure all PDF/PNG files referenced in main.tex are in the book/ directory
+   - LaTeX syntax errors: Check the .log file for line numbers and error context
+   - Missing bibliography: The workflow expects inline bibliography (using `\begin{thebibliography}`)
+
+### Future enhancements
+
+Possible improvements to consider:
+- Add automatic release creation for tagged versions
+- Cache TeX Live packages for faster builds
+- Add PDF validation/linting

.github/workflows/build-book-pdf.yml

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+name: Build Book PDF
+
+# Trigger the workflow on pushes and pull requests to the book branch
+on:
+  push:
+    branches:
+      - book
+    paths:
+      - 'book/**'
+  pull_request:
+    branches:
+      - book
+    paths:
+      - 'book/**'
+  # Allow manual triggering from Actions tab
+  workflow_dispatch:
+
+jobs:
+  build-pdf:
+    runs-on: ubuntu-latest
+
+    permissions:
+      contents: read
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v4
+
+      - name: Compile LaTeX document
+        uses: xu-cheng/latex-action@v3
+        with:
+          root_file: main.tex
+          working_directory: book
+          # Use latexmk for automatic handling of multiple passes
+          args: -pdf -file-line-error -interaction=nonstopmode
+          latexmk_use_lualatex: false
+          latexmk_use_xelatex: false
+          latexmk_shell_escape: false
+
+      - name: Check PDF was created
+        run: |
+          if [ -f book/main.pdf ]; then
+            echo "✓ PDF successfully created"
+            ls -lh book/main.pdf
+          else
+            echo "✗ PDF was not created"
+            exit 1
+          fi
+
+      - name: Upload PDF artifact
+        if: success()
+        uses: actions/upload-artifact@v4
+        with:
+          name: book-pdf
+          path: book/main.pdf
+          retention-days: 90
+
+      - name: Upload LaTeX build logs
+        if: always()
+        uses: actions/upload-artifact@v4
+        with:
+          name: latex-build-logs
+          path: |
+            book/*.log
+            book/*.aux
+            book/*.out
+            book/*.blg
+            book/*.bbl
+            book/*.fls
+            book/*.fdb_latexmk
+          retention-days: 30
+          if-no-files-found: warn