The edge posts the open batch before a failed stream gives the group back

A plain stop and a chunk that doesn't inflate already posted the batch so far,
so the stop snapshot stood at a stored resume point; a failed stream (the
stalled one's "Peer disconnected") skipped the post, left the batch open and
lost the window with the snapshot refused. Now only a batch the coordinator
refused stays open.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

edge/README.md

@@ -248,8 +248,11 @@ COORDINATOR_URL=http://coordinator:3334 NODE_TOKEN=… ./target/release/edge-nod
   snapshot (bincode, gzip) goes to the coordinator every
   `--snapshot-minutes` (EDGE_SNAPSHOT_MINUTES, 30) right after a batch,
   and when the group is given back: caught up (`next` answers 204: the
-  tail), a stop, a lost lease or a failure; the next holder restores it
-  (`GET groups/:id/snapshot`) and continues at its article. `--groups N`
+  tail), a stop, a lost lease or a failure; a stop or a failed stream
+  posts the open batch first, so the snapshot stands at its resume point
+  (a batch the coordinator refused can't, and that window is lost); the
+  next holder restores it (`GET groups/:id/snapshot`) and continues at
+  its article. `--groups N`
   stops after N groups; `--ranges N` is the old per-range lease
   (`POST lease`), one range per thread without a carried window.
 - **As `commands/edge_node.ts`:** retries for network trouble and 5xx;