F-catalog-B: distribution counts incoming against its binding's cap and drops an idle transfer by its expiring key

The holder counted against 20 GiB while the bus caps incoming at 8 GiB, so the bus refused writes before
the holder said refused naming the cap, and the 80 % finding came too late (running review F2). The cap is
read from incoming's binding (the object store's fill); IncomingCap, 8 GiB, is said only where none is read,
and the manifest's row holds it equal to max-mib. An abandoned transfer was dropped only on the next publish,
and the transfers state's own lifetime dropped its key while its parts stayed: transfers keeps for good, and
each open transfer has a key in the new state idle with its own time to live, whose end drops it (re-armed
for the rest when it took a part since). registry_incoming reports the bound cap.

Claude-Session: https://claude.ai/code/session_01JG73KJNrH5EgFXMKKYSrig

modules/distribution/module.json

@@ -83,9 +83,14 @@
     {
       "name": "transfers",
       "storage": "key-value",
+      "template": "state"
+    },
+    {
+      "name": "idle",
+      "storage": "key-value",
       "template": "state",
       "options": {
-        "ttl-seconds": 86400
+        "key-ttl": true
       }
     },
     {