Fix LaTeX/Beamer GHA workflow to fail on first error

Previously the workflow would continue even when generation or
compilation failed, leading to confusing error messages about
missing files. This was caused by:

1. Using || true on generation commands (lines 31-34)
2. Using continue-on-error: true on compilation steps (lines 42,50,58,66)

Fixed by:
- Removing || true to let generation failures fail the workflow
- Removing continue-on-error: true to let compilation failures fail
- Adding verification step to check files exist before compilation

Now the workflow will fail immediately at the first error with a
clear message about what went wrong.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: stared

.github/workflows/test-latex-beamer.yml

@@ -28,42 +28,43 @@ jobs:
 
       - name: Generate LaTeX files
         run: |
-          pnpm tsx test-latex-export-real.ts || true
-          pnpm tsx test-beamer-export.ts || true
-          pnpm tsx test-latex-export-maxwell.ts || true
-          pnpm tsx test-beamer-export-maxwell.ts || true
+          pnpm tsx test-latex-export-real.ts
+          pnpm tsx test-beamer-export.ts
+          pnpm tsx test-latex-export-maxwell.ts
+          pnpm tsx test-beamer-export-maxwell.ts
+
+      - name: Verify generated files exist
+        run: |
+          ls -lh /tmp/test-euler-export.tex /tmp/test-euler-beamer.tex /tmp/test-maxwell.tex /tmp/test-maxwell-beamer.tex
+          echo "All LaTeX files generated successfully"
 
       - name: Compile Euler LaTeX to PDF
         uses: xu-cheng/latex-action@v4
         with:
           root_file: /tmp/test-euler-export.tex
           working_directory: /tmp
           latexmk_use_lualatex: false
-        continue-on-error: true
 
       - name: Compile Euler Beamer to PDF
         uses: xu-cheng/latex-action@v4
         with:
           root_file: /tmp/test-euler-beamer.tex
           working_directory: /tmp
           latexmk_use_lualatex: false
-        continue-on-error: true
 
       - name: Compile Maxwell LaTeX to PDF
         uses: xu-cheng/latex-action@v4
         with:
           root_file: /tmp/test-maxwell.tex
           working_directory: /tmp
           latexmk_use_lualatex: false
-        continue-on-error: true
 
       - name: Compile Maxwell Beamer to PDF
         uses: xu-cheng/latex-action@v4
         with:
           root_file: /tmp/test-maxwell-beamer.tex
           working_directory: /tmp
           latexmk_use_lualatex: false
-        continue-on-error: true
 
       - name: Upload LaTeX artifacts
         uses: actions/upload-artifact@v4