fix: install jupyter in Dockerfile build instead of runtime

- Always install jupyterlab in Dockerfile build (not conditional on DEV_MODE)
- Check jupyter via python import instead of command -v
- Runtime install only as fallback if import fails

Dockerfile

@@ -49,13 +49,10 @@ RUN apt-get update && apt-get install -y \
     xfonts-scalable \
     --no-install-recommends && \
     pip3 install --no-cache-dir --break-system-packages huggingface_hub && \
-    case "$(printf '%s' "${DEV_MODE}" | tr '[:upper:]' '[:lower:]')" in \
-      true|1|yes|on) \
-        pip3 install --no-cache-dir --break-system-packages \
-          jupyterlab==4.5.7 \
-          tornado==6.5.5 \
-          ipywidgets==8.1.8 ;; \
-    esac && \
+    pip3 install --no-cache-dir --break-system-packages \
+      jupyterlab==4.5.7 \
+      tornado==6.5.5 \
+      ipywidgets==8.1.8 && \
     rm -rf /var/lib/apt/lists/*
 
 # Reuse existing node user (UID 1000). Allow passwordless package-manager

start.sh

@@ -749,10 +749,11 @@ if [ -n "${CLOUDFLARE_PROXY_URL:-}" ]; then
   echo "Proxy     : ${CLOUDFLARE_PROXY_URL}"
 fi
 RUNTIME_JUPYTER_ENABLED="$DEV_MODE_ENABLED"
-# Add user bin to PATH for jupyter-lab
+# Add user bin to PATH for jupyter-lab (installed in Dockerfile build)
 export PATH="$HOME/.local/bin:$PATH"
 
-if [ "$DEV_MODE_ENABLED" = "true" ] && ! command -v jupyter-lab >/dev/null 2>&1; then
+# Skip runtime install since jupyter is installed during build
+if [ "$DEV_MODE_ENABLED" = "true" ] && ! python3 -c "import jupyterlab" >/dev/null 2>&1; then
   echo "DEV_MODE enabled but jupyter-lab is missing; attempting runtime install..."
   if python3 -m pip install --user --no-cache-dir --break-system-packages jupyterlab==4.5.7 tornado==6.5.5 ipywidgets==8.1.8; then
     echo "Runtime Jupyter install complete."
@@ -761,7 +762,7 @@ if [ "$DEV_MODE_ENABLED" = "true" ] && ! command -v jupyter-lab >/dev/null 2>&1;
     RUNTIME_JUPYTER_ENABLED=false
   fi
 fi
-if [ "$RUNTIME_JUPYTER_ENABLED" = "true" ] && ! command -v jupyter-lab >/dev/null 2>&1; then
+if [ "$RUNTIME_JUPYTER_ENABLED" = "true" ] && ! python3 -c "import jupyterlab" >/dev/null 2>&1; then
   echo "WARNING: jupyter-lab still unavailable; disabling terminal for this boot."
   RUNTIME_JUPYTER_ENABLED=false
 fi