Add -l/--list-images to discover OCI archives in a directory

list_oci_images() (src/oci_image.cpp) scans a directory non-recursively
for *.tar/*.tar.* files and, for each one that's a valid OCI Image
Layout archive, derives a name:tag from its index.json manifest
annotations -- io.containerd.image.name if present (a full reference),
else org.opencontainers.image.ref.name (conventionally just a bare
tag for skopeo/podman-produced archives). Falls back to the archive's
filename (.tar and any compression suffix stripped) for the name and
"latest" for the tag. Files that aren't OCI archives are skipped
quietly, since a directory scan is expected to hit unrelated tars.

-l/--list-images <directory> wires this into the CLI, printing
"name:tag<TAB>filename" per image. This is also why --log-level lost
its short form last session: -l needed to be free for this.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

CLAUDE.md

@@ -16,9 +16,13 @@ this repo as still early-stage.
 
 Source layout (all under `src/`):
 - `main.cpp` — CLI entry point, dependency checks, orchestration (`mount_image()`,
-  `run_container()`, `cleanup_image()`, `unmount_image()`).
+  `run_container()`, `cleanup_image()`, `unmount_image()`, `list_images_command()`).
 - `oci_image.{h,cpp}` — validates/parses the OCI Image Layout tar (libarchive +
-  nlohmann_json) and extracts layer blobs.
+  nlohmann_json) and extracts layer blobs. `list_oci_images()` scans a directory
+  (non-recursively) for `*.tar`/`*.tar.*` files and, for each valid OCI archive,
+  derives an image name/tag from its `index.json` manifest annotations
+  (`io.containerd.image.name` preferred, else `org.opencontainers.image.ref.name`),
+  falling back to the archive's filename and `"latest"` respectively.
 - `containers_storage.{h,cpp}` — wraps the `containers-storage` CLI (`import-layer`,
   `mount`, `unmount`, `layer --json`, `delete-layer`), forcing `fuse-overlayfs` as the
   overlay `mount_program`. `cleanup_layer_chain()` walks a layer's parent chain
@@ -60,7 +64,8 @@ Build directory is `buildDir/` (already configured).
 - Build: `meson compile -C buildDir` (or `ninja -C buildDir`)
 - Run the executable: `./buildDir/slocker_lite -m <image.tar>` (see `--help` for the
   full flag list: `-m/--mount`, `-r/--run`, `-u/--umount`, `-c/--cleanup`,
-  `-n/--no-nsenter`, `-t/--test`, `-l/--log-level`, `-h/--help`, `-V/--version`)
+  `-l/--list-images`, `-n/--no-nsenter`, `-t/--test`, `--log-level`, `-h/--help`,
+  `-V/--version`)
 - Run tests: `meson test -C buildDir`
 
 ## Code style