daemon: persist teardown fallbacks and reject unsafe import paths

Preserve cleanup after daemon restarts and harden OCI and tar imports
against filenames that debugfs cannot encode safely.

Mirror tap, loop, and dm teardown identity onto VM.Runtime, teach
cleanup and reconcile to fall back to those persisted fields when
handles.json is missing or corrupt, and clear the recovery state on
stop, error, and delete paths.

Reject debugfs-hostile entry names during flattening and in
ApplyOwnership itself, then add regression coverage for corrupt
handles.json recovery and unsafe import paths.

Verified with targeted go tests, make lint-go, make lint-shell, and
make build.

docs/oci-import.md

@@ -28,7 +28,7 @@ banger image pull ghcr.io/myorg/devimg:v2        --kernel-ref generic-6.12
 - Any public OCI image that exposes a `linux/amd64` manifest.
 - Correct layer replay with whiteout semantics (`.wh.*` deletes,
   `.wh..wh..opq` opaque-dir markers).
-- Path-traversal and relative-symlink-escape protection.
+- Path-traversal, debugfs-hostile filename, and relative-symlink-escape protection.
 - Content-aware default sizing (`content × 1.5`, floor 1 GiB).
 - Layer caching on disk, keyed by blob sha256.
 - **Ownership preservation** — tar-header uid/gid/mode captured
@@ -67,8 +67,9 @@ banger image pull ghcr.io/myorg/devimg:v2        --kernel-ref generic-6.12
   `linux/amd64` platform pinned. Layer blobs cache under
   `~/.cache/banger/oci/blobs/` and populate lazily during flatten.
 - **`Flatten`** replays layers oldest-first into a staging directory,
-  applies whiteouts, rejects unsafe paths. Returns a `Metadata` map
-  of per-file uid/gid/mode from tar headers.
+  applies whiteouts, rejects unsafe paths plus filenames that banger's
+  debugfs ownership fixup cannot encode safely. Returns a `Metadata`
+  map of per-file uid/gid/mode from tar headers.
 - **`BuildExt4`** runs `mkfs.ext4 -F -d <staging> -E root_owner=0:0`
   at the size of the pre-truncated file — no mount, no sudo, no
   loopback. Requires `e2fsprogs ≥ 1.43`.