recent-files list: designer raise/sink scrollbar

The framed recent-files region adopts the toolkit ScrollRegion's
sink-behind mode, self-contained in push_prims: idle the bar is a dim
ghost under the well's translucent fill, scrolling raises it, 0.7s of
quiet sinks it back. Rows keep clear of the bar's gutter, so the framed
draw order needs no change.

Co-Authored-By: Claude Fable 5 <[email protected]>

 src/main.rs | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/src/main.rs b/src/main.rs
index c2e4910..d5dad2a 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -2392,6 +2392,8 @@ impl LayoutApp {
             0 => {
                 if self.btn_new_doc.tick(dt, ctx) { changed = true; }
                 if self.btn_open.tick(dt, ctx) { changed = true; }
+                // Raise/sink upkeep for the recent-files scrollbar.
+                if self.recent_files_list.tick(dt) { changed = true; }
                 for btn in &mut self.recent_files_buttons {
                     if btn.tick(dt, ctx) { changed = true; }
                 }
@@ -2745,7 +2747,10 @@ impl Application for LayoutApp {
         label_total_elements.set_rect(0.0, 0.0, 240.0, 18.0);
 
         let recent_files = Self::load_recent_files();
-        let recent_files_list = ScrollRegion::new(22.0, 2.0);
+        // Designer raise/sink treatment, self-contained for a framed region:
+        // push_prims lays the sunk bar under the translucent bg fill (a dim
+        // ghost inside the well) and the raised bar on top while scrolling.
+        let recent_files_list = ScrollRegion::new(22.0, 2.0).with_sink_behind(true);
         let mut recent_files_buttons = Vec::new();
         for file in &recent_files {
             let label = file.file_name()