the addon survey seats a populated world, and hidden frames arrive

- the corpus harness now seats a buff, a target and a ticking cooldown instead of an empty world, so "nothing to draw" and "failed to draw" stop sharing a row — and the richer seat immediately exposed two real gaps
- an addon button inheriting our action-button template now works even when it replaces the template's OnLoad: the handlers resolve their regions by name, the way the reference does on every access
- more of the reference's hidden-by-default frames exist by name — ReputationWatchBar, MiniMapBattlefieldFrame, MiniMapMeetingStoneFrame — for the addons that reposition them
- StartSizing lands beside its stop verb, and the sourced bag-anchor code runs against windows we actually build

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

crates/benilla-ui/src/script/pointer.rs

@@ -204,6 +204,7 @@ impl UiScript {
             // crosses and a pump behind the early return would only ever advance when the cursor
             // left the frame it is dragging.
             super::object::advance_move(&mut model, (x, y));
+            super::object::advance_size(&mut model, (x, y));
             let drag_start = cursor::maybe_start_drag(&mut model, (x, y));
             let new_handle = new_id.and_then(|id| model.id_to_frame.get(&id).copied());
             if new_handle == model.mouseover {