docs: edit-flow section reads clean under the prose lint

docs/swarm/ui.md

@@ -248,18 +248,19 @@ ends. Pick a node to edit it in the panel beside the canvas:
   text can use `{field}` placeholders.
 
 Beside the fields, **add a match below** and **add a todo below** grow the
-branch, **move under** moves a node and what is below it to another match, and
-**remove** takes a node and its branch out. The editor turns away what could
-never be saved, with the reason: a todo with children, a second parent, a node
-under its own branch, or more nodes or levels than the controller allows.
+branch, **move under** moves a node and what's below it to another match, and
+**remove** takes a node and its branch out. The editor turns away any edit the
+controller would refuse to save, and says why: a todo with children, a second
+parent, a node under its own branch, or more nodes or levels than the
+controller allows.
 
 Edits stay in a draft until **save**, which sends the whole flows document with
 the revision the editor read. **discard edits** goes back to the saved flow and
-**delete flow** removes it, after a confirmation. If the flows were changed
-somewhere else in the meantime the save is refused as stale, and the editor
-offers to reload and drop your edits, or to keep them on top of the latest. A
-document the controller refuses for any other reason is shown as the controller
-says. The router runs a saved flow from its next event.
+**delete flow** removes it, after a confirmation. If someone changed the flows
+elsewhere in the meantime, the controller turns the save down as stale, and the
+editor offers to reload and drop your edits, or to keep them on top of the
+latest. For any other refusal the editor shows the controller's own message.
+The router runs a saved flow from its next event.
 
 ### Sending a message to an agent