Merge forge/main into atlas/5034-s4-remove-hive-model

docs/web-ui/agent.md

@@ -162,6 +162,9 @@ select-all / select-none / `✓ mark done` bulk row above the list POSTs
 the checked ids to `POST /api/todos/mark-done`, which dismisses them
 from the harness-local store (same effect as `cancel_loose_end(kind:
 "todo")`, just from the web UI instead of the agent's own tool calls).
+If the todo store errors or doesn't answer for any id, the endpoint returns
+500 naming how many ids failed, and the panel shows `failed: …` instead of
+`✓ marked done`.
 
 ## Live view