Add LaTeX build log artifacts for debugging compilation failures

.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
+   - Artifacts are available for download from the Actions tab for 90 days
+   - Each workflow run creates a `book-pdf` artifact containing `main.pdf`
+
+### Accessing the PDF
+
+After a successful build:
+
+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 `book-pdf` artifact (will be a .zip file containing main.pdf)
+
+### Accessing build logs for debugging
+
+For every workflow run (successful or failed), LaTeX build logs are automatically uploaded:
+
+1. Go to the **Actions** tab in the GitHub repository
+2. Click on the workflow run you want to debug
+3. Scroll down to the **Artifacts** section
+4. Download the `latex-logs` artifact (will be a .zip file containing log files)
+5. The artifact includes:
+   - `main.log` - Main LaTeX compilation log with detailed error messages
+   - `main.aux` - Auxiliary file with cross-references
+   - `main.out` - Hyperref output file
+   - `main.toc` - Table of contents data
+   - `main.bbl` - Bibliography file (if generated)
+   - `main.blg` - Bibliography log (if generated)
+
+The `main.log` file is especially useful for debugging compilation errors, as it contains:
+- Line numbers where errors occurred
+- Detailed error messages from LaTeX
+- Warnings about missing packages, figures, or references
+- Information about which files were processed
+
+### 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 `latex-logs` artifact from the Actions tab (see "Accessing build logs" above)
+2. Open `main.log` to see detailed error messages with line numbers
+3. Check the workflow logs in the Actions tab for the summary output
+4. Common issues:
+   - Missing figures: Ensure all PDF/PNG files referenced in main.tex are in the book/ directory
+   - LaTeX syntax errors: Check main.log for the specific line number and error message
+   - Missing bibliography: The workflow expects inline bibliography (using `\begin{thebibliography}`)
+   - Package conflicts: Check main.log for package loading errors or conflicts
+
+### Future enhancements
+
+Possible improvements to consider:
+- Add automatic release creation for tagged versions
+- Cache TeX Live packages for faster builds
+- Add PDF validation/linting
+- Generate HTML or other output formats alongside PDF

.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-logs
+          path: |
+            book/*.log
+            book/*.aux
+            book/*.out
+            book/*.toc
+            book/*.blg
+            book/*.bbl
+          retention-days: 30
+          if-no-files-found: warn