Install python-docx before the CI backend tests

Why: The runner image has Python but not python-docx, so TestLintErrorContinues failed after checkout succeeded.
Evidence: Agent-System-Dev actions job 1012 reported ModuleNotFoundError: No module named docx.
Impact: The package comes from the Tsinghua PyPI mirror. Library CI still stops until SUBMODULE_TOKEN is set.
Refs: feature/agent-stack-r0-r1
Co-authored-by: Cursor <cursoragent@cursor.com>

.gitea/workflows/ci.yaml

@@ -39,6 +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: make test (boundaries, pins, libs, core, backend, frontend, ui, agent-command)
         run: make test
       - name: Build the single binary