Use direct kubectl release download in devcontainer

Agent-Logs-Url: https://github.com/cloudengine-labs/devops_os/sessions/8929bee2-ec5e-454a-8614-f771484942ab

Co-authored-by: chefgs <7605658+chefgs@users.noreply.github.com>

Author: Copilot

.devcontainer/Dockerfile

@@ -123,11 +123,12 @@ RUN if [ "$INSTALL_TERRAFORM" = "true" ]; then \
 
 # Install kubectl if requested
 RUN if [ "$INSTALL_KUBECTL" = "true" ]; then \
-    KUBECTL_CHANNEL="$(curl -fsSL https://dl.k8s.io/release/stable.txt | sed -E 's/^v([0-9]+\.[0-9]+).*/v\1/')" \
-    && curl -fsSL "https://pkgs.k8s.io/core:/stable:/${KUBECTL_CHANNEL}/deb/Release.key" | gpg --dearmor -o /usr/share/keyrings/kubernetes-apt-keyring.gpg \
-    && echo "deb [signed-by=/usr/share/keyrings/kubernetes-apt-keyring.gpg] https://pkgs.k8s.io/core:/stable:/${KUBECTL_CHANNEL}/deb/ /" > /etc/apt/sources.list.d/kubernetes.list \
-    && apt-get update \
-    && apt-get install -y kubectl; \
+    KUBECTL_VERSION="$(curl -fsSL https://dl.k8s.io/release/stable.txt)" \
+    && curl -fsSLo /tmp/kubectl "https://dl.k8s.io/release/${KUBECTL_VERSION}/bin/linux/amd64/kubectl" \
+    && curl -fsSLo /tmp/kubectl.sha256 "https://dl.k8s.io/release/${KUBECTL_VERSION}/bin/linux/amd64/kubectl.sha256" \
+    && echo "$(cat /tmp/kubectl.sha256)  /tmp/kubectl" | sha256sum --check \
+    && install -o root -g root -m 0755 /tmp/kubectl /usr/local/bin/kubectl \
+    && rm -f /tmp/kubectl /tmp/kubectl.sha256; \
     fi
 
 # Install Helm if requested