TODO: a prepare stage on Event, for the placeholder in CursorData

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

TODO

@@ -24,3 +24,17 @@ transforms on a move entry (scale + rotation)
     write and no redraw
     wanted for compose-style stretch at the end of a scroll area, and for
     rotation generally
+
+a prepare stage on Event, so Data has no placeholder field
+    run_sensors builds one CursorData per widget and has to put something in
+    `sense` before anything knows which sense matched, so it writes
+    CursorSense::Hovering and says in place that it means nothing;
+    should_run then clones the whole thing to overwrite that one field
+    the state is representable only because the type lets the caller say it:
+    what the caller supplies and what matching adds are two different things
+    wearing one struct
+    the awkward part is doing it without the generics getting annoying --
+    Data<'a> is already a GAT with a default, and splitting it in two adds
+    another associated type to every Event impl for the sake of one field
+    (Bryan, 2026-09-20; low priority, he wants a good answer rather than a
+    quick one)