RegisterEvent ignores case; a frame's first resize precedes OnLoad (#1001)

- `RegisterEvent` and `UnregisterEvent` match a name against the client's event table case-insensitively and drop a name that isn't in it (`0x702140`). A new gate checks that every event name the code fires is in the table.
- A visible XML frame resolves its layout at the post-load hook (`0x76a310` → `0x7680e0(1)`). So its first `OnSizeChanged` fires before its `<Frames>`, `OnLoad` and `OnShow`, as in 1.12.1. A hidden frame still waits for its show.
- `pending_events`' doc now says what the queue is: `SignalEvent` (`0x703e50`) runs handlers in place, and the Lua verbs that still queue are a gap.
- #890 was already fixed by #907; two stale comments around it are corrected.

Fixes #959
Fixes #972
Fixes #560
Closes #890

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

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

@@ -643,7 +643,8 @@ pub(super) fn create_frame(
         // The builder's pre-load and post-load hooks (`0x6ee4d6`, `0x6ee4ea`): a frame born hidden
         // is deferred, as a hidden parent leaves it. A template's load opens its own window.
         model.layout_load_begin(h);
-        model.layout_load_end(h);
+        // No handler is bound yet, so the resolve this owes fires nothing.
+        let _ = model.layout_load_end(h);
         id
     };