fix: add modloop= to cmdline, revert lz4 compression

modloop was not mounting because:
1. modloop=/boot/modloop-lts was missing from kernel cmdline
2. lz4-compressed squashfs may not be supported by Alpine initramfs

Both issues result in /lib/modules not existing and all modprobe failing.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

iso/builder/build-debug.sh

@@ -27,10 +27,8 @@ done
 . "${BUILDER_DIR}/VERSIONS"
 export PATH="$PATH:/usr/local/go/bin"
 
-# Use lz4 for mksquashfs — much faster than xz, size difference is negligible for RAM-loaded modloop.
-mkdir -p /etc/mkinitfs
-grep -q 'MKSQUASHFS_OPTS' /etc/mkinitfs/mkinitfs.conf 2>/dev/null || \
-    echo 'MKSQUASHFS_OPTS="-comp lz4 -Xhc"' >> /etc/mkinitfs/mkinitfs.conf
+# NOTE: lz4 compression for modloop is disabled — Alpine initramfs may not support lz4 squashfs.
+# Default xz compression is used until lz4 support is confirmed.
 
 echo "=== bee debug ISO build ==="
 echo "Alpine: ${ALPINE_VERSION}, Go: ${GO_VERSION}"