Fix layout cache correctness and GPU resource recovery

src/app/mod.rs

@@ -1055,14 +1055,7 @@ pub(super) struct OpenCADStudio {
     /// `Some` while a CAD file is loading — drives the modal overlay.
     /// Cleared when the load finishes, errors, or the user cancels.
     pub(super) opening: Option<OpenProgress>,
-    /// Set the moment a layout switch changes `current_layout`, cleared on the
-    /// next presented frame.
-    ///
-    /// The switch itself costs about 10 ms; the frame after it rebuilds the
-    /// whole wire set and can block the main thread for seconds. While this is
-    /// set the viewport is replaced by a notice, so that frame is cheap — which
-    /// gives the compositor an answer, and the user something other than a
-    /// stale window, immediately before the expensive one.
+    /// Show a lightweight notice until the next layout redraw.
     pub(super) layout_settling: bool,
     open_job_serial: u64,
     /// Last repair or failed-open report shown in the recovery modal.
@@ -2292,8 +2285,7 @@ pub enum Message {
     /// Timer pulse while the cursor is dwelling on a grip; drives the
     /// dwell-to-popup transition without requiring further mouse motion.
     GripDwellTick,
-    /// One frame has been presented since a layout switch; the next may do the
-    /// expensive rebuild.
+    /// The notice redraw allows the next frame to build the scene.
     LayoutSettled,
     /// Timer pulse while a rollover hit-test is queued; fires when the
     /// cursor has been still long enough to safely run the pick.