Reverts commits 79908b3c6, 083c5a042, e1ff75624, ff77fa248. (#3496)

The non-root user approach had multiple issues with RunPod
compatibility, sudo PATH handling, and tmux in exec sessions.
Restoring root as the default user for now.

docker/Dockerfile-uv-base

@@ -17,19 +17,13 @@ ENV TORCH_CUDA_ARCH_LIST=$TORCH_CUDA_ARCH_LIST
 ENV UV_TORCH_BACKEND="cu${CUDA}"
 
 RUN apt-get update \
-    && apt-get install -y wget git build-essential ninja-build git-lfs libaio-dev pkg-config curl sudo && rm -rf /var/lib/apt/lists/* \
+    && apt-get install -y wget git build-essential ninja-build git-lfs libaio-dev pkg-config curl && rm -rf /var/lib/apt/lists/* \
     && git lfs install --skip-repo \
-    && curl -LsSf https://astral.sh/uv/install.sh | env UV_INSTALL_DIR="/usr/local/bin" sh
+    && curl -LsSf https://astral.sh/uv/install.sh | sh
 
-# Create ubuntu user with passwordless sudo
-RUN useradd -m -s /bin/bash -u 1000 ubuntu 2>/dev/null; \
-    usermod -aG sudo ubuntu && \
-    echo 'ubuntu ALL=(ALL) NOPASSWD:ALL' > /etc/sudoers.d/ubuntu && \
-    chmod 0440 /etc/sudoers.d/ubuntu
+ENV PATH="/root/.local/bin:${PATH}"
 
-ENV UV_PYTHON_INSTALL_DIR="/opt/uv/python"
-RUN uv python install ${PYTHON_VERSION} && \
-    chmod -R a+rX /opt/uv
+RUN uv python install ${PYTHON_VERSION}
 
 WORKDIR /workspace
 
@@ -61,5 +55,3 @@ RUN PYTHON_CP="cp$(echo $PYTHON_VERSION | tr -d '.')" && \
     wget -nv "https://github.com/mjun0812/flash-attention-prebuild-wheels/releases/download/${WHL_VERSION}/${WHL_FILE}" && \
     uv pip install --no-cache-dir "${WHL_FILE}" && \
     rm "${WHL_FILE}"
-
-RUN chown -R ubuntu:ubuntu /workspace