test(modules): pin orphan-sweep coverage of group-shared blobs (§11.6 files review)

The §11.6 files slice relies on the orphan sweeper covering the new
`files/groups/<group_id>/...` subtree "for free" via its recursive walk
of `<root>/files/`, with no sweeper code change. Lock that guarantee
with an explicit test so a future sweeper refactor can't silently drop
group-shared tmp files.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/manager-core/src/files_sweep.rs

@@ -165,6 +165,23 @@ mod tests {
         assert!(tmp.exists());
     }
 
+    #[test]
+    fn sweeps_group_shared_tmp_files() {
+        // §11.6 group-shared files shard under `files/groups/<group_id>/...`,
+        // a disjoint subtree from the per-app `files/<app_id>/...`. The walk is
+        // recursive from `<root>/files/`, so an orphan there is reaped without
+        // any group-specific sweeper change — this pins that "covered for free"
+        // guarantee against a future refactor.
+        let root = tmp_root();
+        let group_shard = root.join("files/groups/6f693a33-9ae5-485b-804e-191e9fd33524/assets/ab");
+        std::fs::create_dir_all(&group_shard).unwrap();
+        let tmp = group_shard.join("uuid.tmp.123-0");
+        touch(&tmp);
+        let stats = sweep_orphan_tmp_files(&root, Duration::ZERO);
+        assert_eq!(stats.files_deleted, 1, "group-shared orphan must be reaped");
+        assert!(!tmp.exists());
+    }
+
     #[test]
     fn keeps_non_tmp_files() {
         let root = tmp_root();