ScriptUI: a docked panel gets its dock's size and onResize (#2585)

A docked ScriptUI panel only ever saw its preferredSize: the host drew
it in a scroll area at max(dock, preferred) and the script's window never
learned the dock. scriptui.resize now gives a window a size: the script's
window takes it, lays itself out again and runs onResizing / onResize.
The dock host sends it whenever the panel's dock size changes, so
window.size is the dock's, as in After Effects.

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

crates/engine/src/cmd/scripts.rs

@@ -467,6 +467,15 @@ pub fn specs() -> Vec<CommandSpec> {
             always,
             scriptui::mouse
         ),
+        cmd!(
+            "scriptui.resize",
+            "Resize Script Window",
+            [],
+            None,
+            "{window?, size: [width, height] (pixels)} → the window takes the size, lays itself out again and its onResizing / onResize run (a docked ScriptUI panel gets its dock's size)",
+            always,
+            scriptui::resize
+        ),
         cmd!(
             "scriptui.close",
             "Close Script Window",