Install the house-style Python packages in CI

Why: lint.py imports python-pptx and openpyxl at import time, so installing only python-docx still skipped the layout finding.
Evidence: actions run 680 failed TestLintErrorContinues with lint reason missing after python-docx was present.
Impact: CI installs python-docx, python-pptx, and openpyxl from the Tsinghua index.
Refs: feature/agent-stack-r0-r1
Co-authored-by: Cursor <cursoragent@cursor.com>

.gitea/workflows/ci.yaml

@@ -39,8 +39,8 @@ jobs:
           set -euo pipefail
           curl -fsSL -o "$RUNNER_TEMP/node.tar.xz" https://npmmirror.com/mirrors/node/v22.23.3/node-v22.23.3-linux-x64.tar.xz
           tar -C /usr/local --strip-components=1 -xJf "$RUNNER_TEMP/node.tar.xz"
-      - name: Install python-docx for backend lint tests
-        run: python3 -m pip install --break-system-packages -i https://pypi.tuna.tsinghua.edu.cn/simple python-docx
+      - name: Install house-style Python packages
+        run: python3 -m pip install --break-system-packages -i https://pypi.tuna.tsinghua.edu.cn/simple python-docx python-pptx openpyxl
       - name: make test (boundaries, pins, libs, core, backend, frontend, ui, agent-command)
         run: make test
       - name: Build the single binary