fix(media): a sweep carries the emptied folder's own empty subfolders

The live sweep removed 2271 husks and left 146 standing, every one a release
folder blocked by a junk subfolder (Screens/, Sample/, a BDMV leaf) that no
file ever moved out of. Eligibility was per-folder, so the blocker was never a
target and its parent could never be removed.

Proof now carries downward: inside a folder the journal shows emptied, every
empty directory qualifies. Nothing under such a folder can hold data, and every
removal is still journalled as rmdir and undone by rollback.

The new test is red against the previous revision, green now. The live sweep
touched no file: 8193 before, 8193 after.

scripts/media-apply.py

@@ -241,6 +241,11 @@ def sweep_targets(root, journal):
     journalled destination lives under it. A symlink anywhere inside disqualifies
     the whole subtree: this tool never follows a link, and deleting the folder
     that holds one would delete someone's mount point.
+
+    Proof carries downward: once a folder qualifies, every empty directory inside
+    it qualifies too. A release's junk (``Screens/``, ``Sample/``) is never itself
+    a move source, so without that rule it holds its emptied parent on disk
+    forever — the parent can never be removed while the child stands.
     """
     moves = [r for r in journal.records if r.get("op") == "move"]
     made = {r["dst"] for r in journal.records if r.get("op") == "mkdir"}
@@ -268,8 +273,15 @@ def sweep_targets(root, journal):
                 return False
         return True
 
-    return sorted((d for d in marked if removable(d)),
-                  key=lambda q: (-q.count(os.sep), q))
+    roots = [d for d in marked if removable(d)]
+    targets = set(roots)
+    for d in roots:
+        for dirpath, dirnames, _ in os.walk(d):
+            for c in dirnames:
+                p = os.path.join(dirpath, c)
+                if removable(p):
+                    targets.add(p)
+    return sorted(targets, key=lambda q: (-q.count(os.sep), q))
 
 
 def do_sweep(args, root, journal):