ci: remove GitHub CI — native git.hanzo.ai + cd.hanzo.ai only

This workflow ran on a self-hosted actions-runner-controller pool. ARC is
being decommissioned: CI executes inside git.hanzo.ai (Gitea Actions,
.hanzo/workflows) and delivery is cd.hanzo.ai reconciling the reviewed image
pin in hanzoai/universe. GitHub is a mirror and runs nothing.

Removed rather than repointed — there is no GitHub-side pool to move to, and
leaving it would keep ARC load-bearing.

.github/workflows/build-papers.yml

@@ -1,98 +0,0 @@
-name: Build LaTeX Papers
-
-on:
-  push:
-    branches: [ main ]
-    paths:
-      - '**.tex'
-      - '**.bib'
-      - 'Makefile'
-      - '.github/workflows/build-papers.yml'
-  pull_request:
-    branches: [ main ]
-    paths:
-      - '**.tex'
-      - '**.bib'
-      - 'Makefile'
-  workflow_dispatch:
-
-permissions:
-  contents: write
-
-jobs:
-  build-pdfs:
-    runs-on: hanzo-build-linux-amd64
-
-    steps:
-      - name: Checkout repository
-        uses: actions/checkout@v4
-        with:
-          fetch-depth: 0
-
-      - name: Install LaTeX
-        run: |
-          sudo apt-get update
-          sudo apt-get install -y texlive-full
-
-      - name: Compile all papers
-        run: |
-          make all
-
-          # Defense papers (separate style)
-          mkdir -p pdfs/defense
-          cd defense
-          for texfile in *.tex; do
-            [ "$texfile" = "hanzo-defense.sty" ] && continue
-            [ "$texfile" = "logo-convert.tex" ] && continue
-            basename="${texfile%.tex}"
-            echo "Compiling defense/$texfile..."
-            pdflatex -interaction=nonstopmode "$texfile" || true
-            bibtex "$basename" 2>/dev/null || true
-            pdflatex -interaction=nonstopmode "$texfile" || true
-            pdflatex -interaction=nonstopmode "$texfile" || true
-            [ -f "${basename}.pdf" ] && cp "${basename}.pdf" ../pdfs/defense/ && echo "  OK defense/${basename}.pdf" || echo "  FAIL defense/${basename}.pdf"
-            rm -f *.aux *.log *.bbl *.blg *.out *.toc
-          done
-          cd ..
-
-      - name: List generated PDFs
-        run: find pdfs -name '*.pdf' | sort
-
-      - name: Upload PDFs as artifacts
-        uses: actions/upload-artifact@v4
-        with:
-          name: hanzo-papers
-          path: |
-            pdfs/*.pdf
-            pdfs/zen/*.pdf
-            pdfs/defense/*.pdf
-          retention-days: 90
-
-      - name: Create release with PDFs
-        if: github.event_name == 'push' && github.ref == 'refs/heads/main'
-        uses: softprops/action-gh-release@v2
-        with:
-          tag_name: v${{ github.run_number }}
-          name: "Hanzo Papers Build #${{ github.run_number }}"
-          files: |
-            pdfs/*.pdf
-            pdfs/zen/*.pdf
-            pdfs/defense/*.pdf
-          make_latest: true
-        env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
-
-      - name: Commit PDFs back to repository
-        if: github.event_name == 'push' && github.ref == 'refs/heads/main'
-        run: |
-          git config --local user.email "github-actions[bot]@users.noreply.github.com"
-          git config --local user.name "github-actions[bot]"
-
-          git add pdfs/*.pdf pdfs/zen/*.pdf pdfs/defense/*.pdf 2>/dev/null || true
-
-          if git diff --staged --quiet; then
-            echo "No changes to commit"
-          else
-            git commit -m "Auto-generated PDFs from LaTeX sources [skip ci]"
-            git push
-          fi