用 marknb 替换 Python markdown，并添加一键安装与升级脚本。

部署时通过 install.sh 自动编译 marknb；日常更新用 upgrade.sh 拉代码并重编译。

Co-authored-by: Cursor <cursoragent@cursor.com>

.cnb.yml

@@ -3,11 +3,5 @@ $:
     - runner:
         cpus: 2
       stages:
-        - name: ls
-          script: ls -al
-        - name: install dependents
-          script: 
-            - apt install python3 python3-pip python3-venv -y
-            - python3 -m venv ./venv
-            - ./venv/bin/pip install -r requirements.txt
-            - echo "source $(pwd)/venv/bin/activate" >> ~/.zshrc
+        - name: install
+          script: bash scripts/install.sh