Drop legacy non-container builders

iso/builder/build.sh

@@ -1,14 +1,13 @@
 #!/bin/sh
-# build.sh — build bee ISO (Debian 12 / live-build)
-#
-# Single build script. Produces a bootable live ISO with SSH access, TUI, NVIDIA drivers.
-#
-# Run on Debian 12 builder VM as root after setup-builder.sh.
-# Usage:
-#   sh iso/builder/build.sh [--authorized-keys /path/to/authorized_keys]
+# build.sh — internal ISO build entrypoint executed inside the builder container.
 
 set -e
 
+if [ "${BEE_CONTAINER_BUILD:-0}" != "1" ]; then
+    echo "build.sh must run inside iso/builder/build-in-container.sh" >&2
+    exit 1
+fi
+
 REPO_ROOT="$(cd "$(dirname "$0")/../.." && pwd)"
 BUILDER_DIR="${REPO_ROOT}/iso/builder"
 OVERLAY_DIR="${REPO_ROOT}/iso/overlay"