Phase 3: banger kernel import bridges make-*-kernel.sh output

`banger kernel import <name> --from <dir>` copies a staged kernel
bundle into the local catalog. <dir> is the output of
`make void-kernel` or `make alpine-kernel` (build/manual/void-kernel/
or build/manual/alpine-kernel/).

kernelcat.DiscoverPaths locates artifacts under <dir>:
 1. Prefers metadata.json (written by make-void-kernel.sh).
 2. Falls back to globbing: boot/vmlinux-* or vmlinuz-* (Alpine
    fallback), boot/initramfs-*, lib/modules/<latest>.

The daemon's KernelImport copies kernel + optional initrd via
system.CopyFilePreferClone and modules via system.CopyDirContents
(no-sudo mode — catalog lives under ~/.local/state), computes SHA256
over the kernel, and writes the manifest via kernelcat.WriteLocal.

While wiring this up, fixed a latent bug in system.CopyDirContents:
filepath.Join(sourceDir, ".") silently drops the trailing dot, so
`cp -a source source/contents target/` was copying the whole source
directory (including its basename) instead of just its contents.
Replaced the join with a manual "/." suffix. imagemgr.StageBootArtifacts
(the only existing caller) silently benefits.

scripts/register-void-image.sh and scripts/register-alpine-image.sh
are rewritten to use `banger kernel import … && banger image register
--kernel-ref …` instead of the find-and-pass-paths dance. Preserves
the same user-facing commands and env vars.

Tests cover: metadata.json preference, glob fallback, Alpine vmlinuz
fallback, kernel-missing error, round-trip copy into the catalog, and
the --from required flag.

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

scripts/register-void-image.sh

@@ -5,23 +5,6 @@ log() {
   printf '[register-void-image] %s\n' "$*" >&2
 }
 
-find_latest_matching() {
-  local dir="$1"
-  local pattern="$2"
-  if [[ ! -d "$dir" ]]; then
-    return 1
-  fi
-  find "$dir" -maxdepth 1 -type f -name "$pattern" | sort | tail -n 1
-}
-
-find_latest_module_dir() {
-  local root="$1"
-  if [[ ! -d "$root" ]]; then
-    return 1
-  fi
-  find "$root" -mindepth 1 -maxdepth 1 -type d | sort | tail -n 1
-}
-
 resolve_banger_bin() {
   if [[ -n "${BANGER_BIN:-}" ]]; then
     printf '%s\n' "$BANGER_BIN"
@@ -47,6 +30,7 @@ SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 REPO_ROOT="$(cd "$SCRIPT_DIR/.." && pwd)"
 RUNTIME_DIR="${BANGER_MANUAL_DIR:-$REPO_ROOT/build/manual}"
 IMAGE_NAME="${VOID_IMAGE_NAME:-void}"
+KERNEL_REF="${VOID_KERNEL_REF:-$IMAGE_NAME}"
 BANGER_BIN="$(resolve_banger_bin)"
 ROOTFS="$RUNTIME_DIR/rootfs-void.ext4"
 WORK_SEED="$RUNTIME_DIR/rootfs-void.work-seed.ext4"
@@ -59,30 +43,21 @@ if [[ ! -f "$WORK_SEED" ]]; then
   log "missing Void work-seed: $WORK_SEED"
   exit 1
 fi
-
-args=(
-  image register
-  --name "$IMAGE_NAME"
-  --rootfs "$ROOTFS"
-  --work-seed "$WORK_SEED"
-)
-
 if [[ ! -d "$RUNTIME_DIR/void-kernel" ]]; then
   log "missing staged Void kernel artifacts: $RUNTIME_DIR/void-kernel"
   log "run 'make void-kernel' before registering $IMAGE_NAME"
   exit 1
 fi
 
-kernel="$(find_latest_matching "$RUNTIME_DIR/void-kernel/boot" 'vmlinux-*' || true)"
-initrd="$(find_latest_matching "$RUNTIME_DIR/void-kernel/boot" 'initramfs-*' || true)"
-modules="$(find_latest_module_dir "$RUNTIME_DIR/void-kernel/lib/modules" || true)"
+log "importing Void kernel from $RUNTIME_DIR/void-kernel as $KERNEL_REF"
+"$BANGER_BIN" kernel import "$KERNEL_REF" \
+  --from "$RUNTIME_DIR/void-kernel" \
+  --distro void \
+  --arch x86_64
 
-if [[ -z "$kernel" || -z "$initrd" || -z "$modules" ]]; then
-  log "staged Void kernel is incomplete; expected vmlinux, initramfs, and modules under $RUNTIME_DIR/void-kernel"
-  exit 1
-fi
-
-log "using staged Void kernel artifacts from $RUNTIME_DIR/void-kernel"
-args+=(--kernel "$kernel" --initrd "$initrd" --modules "$modules")
-
-"$BANGER_BIN" "${args[@]}"
+log "registering image $IMAGE_NAME with kernel-ref $KERNEL_REF"
+"$BANGER_BIN" image register \
+  --name "$IMAGE_NAME" \
+  --rootfs "$ROOTFS" \
+  --work-seed "$WORK_SEED" \
+  --kernel-ref "$KERNEL_REF"