fix(sftp): give the transfers list its scrollbar too

The last scroll area in the app without one. It caps at 200px and
scrolls past it, so eight queued downloads run off the bottom edge with
nothing to say so.

The shared helper grows into a flex parent, which is wrong for a box
that already carries its own height — taking flex_1 there would stretch
it past its cap or collapse it, which is why this one had been left
alone. `over_vertical_scroll` lays the same bar over an area that
measured itself, so the layout is exactly what it was without it.

Verified over a real SSH connection to localhost: queued eight
downloads, confirmed the list still scrolls through them and the bar
renders.

src/ui/scrollbar.rs

@@ -41,3 +41,30 @@ pub(crate) fn with_vertical_scrollbar(
         )
         .into_any_element()
 }
+
+/// The same bar, for a scroll area that already carries its own height —
+/// a `max_h` box, say.
+///
+/// `with_vertical_scrollbar` grows into a flex parent, which is wrong for a box
+/// that is already the size it wants to be: taking `flex_1` there would either
+/// stretch it past its cap or collapse it. This wrapper only lays the bar over
+/// whatever the area measured, so the layout is exactly what it was without it.
+pub(crate) fn over_vertical_scroll(
+    id: impl Into<ElementId>,
+    scroll_area: impl IntoElement,
+    handle: &ScrollHandle,
+) -> AnyElement {
+    div()
+        .relative()
+        .child(scroll_area)
+        .child(
+            div()
+                .absolute()
+                .top_0()
+                .left_0()
+                .right_0()
+                .bottom_0()
+                .child(Scrollbar::vertical(handle).id(id)),
+        )
+        .into_any_element()
+}

src/ui/sftp.rs

@@ -151,6 +151,7 @@ pub(crate) struct SftpPanelState {
     editing_path_sub: Vec<Subscription>,
     pub(crate) poll_gen: u64,
     scroll: gpui::ScrollHandle,
+    transfers_scroll: gpui::ScrollHandle,
     _subs: Vec<Subscription>,
 }
 
@@ -184,6 +185,7 @@ impl SftpPanelState {
             editing_path_sub: Vec::new(),
             poll_gen: 0,
             scroll: gpui::ScrollHandle::new(),
+            transfers_scroll: gpui::ScrollHandle::new(),
             _subs: vec![sub],
         }
     }
@@ -1554,11 +1556,19 @@ impl Tty7App {
                 }
                 list
             };
-            div()
-                .id("sftp-transfers-list")
-                .max_h(px(200.))
-                .overflow_y_scroll()
-                .child(inner)
+            // The list caps at 200px and scrolls past it; it was the last
+            // scroll area in the app with nothing to say so. This wrapper only
+            // overlays the bar, so the box keeps the height it already had.
+            crate::ui::scrollbar::over_vertical_scroll(
+                "sftp-transfers-scrollbar",
+                div()
+                    .id("sftp-transfers-list")
+                    .max_h(px(200.))
+                    .overflow_y_scroll()
+                    .track_scroll(&self.sftp_panel.transfers_scroll)
+                    .child(inner),
+                &self.sftp_panel.transfers_scroll,
+            )
         });
 
         Some(