Split: no separator line, just the gap between the plates

Two plates with a 20px gap already read as two panes; a 1px line drawn
down the middle of that gap was chrome saying what the gap says. Drop it.

The split stays draggable in the gap, and the resize cursor over the grab
band is now the whole affordance — which is why cursor_icon's band, not
the line, was always the thing that mattered.

Co-Authored-By: Claude Fable 5.1 <[email protected]>

 src/main.rs | 17 ++++++++++-------
 1 file changed, 10 insertions(+), 7 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index 2c808e9..34a3c6a 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -4556,7 +4556,7 @@ impl Application for ClearEmailApp {
         let current_folder_str = self.current_folder.clone();
 
         let list_x = LIST_X;
-        let (list_w, separator_x, detail_x) = self.split_geom();
+        let (list_w, _separator_x, detail_x) = self.split_geom();
 
         if self.needs_rebuild || size_changed {
             // Bar layout — every open dropdown is a popover: registration
@@ -4752,8 +4752,11 @@ impl Application for ClearEmailApp {
         cce_ui::scene::painter::paint_root_into(&self.ui_context, &self.folder_dropdown, &mut *quads.pc);
         cce_ui::scene::painter::paint_root_into(&self.ui_context, &self.account_dropdown, &mut *quads.pc);
 
-        // 3. The detail pane's plate, and the separator seam between the two.
-        // Same fill and same radius as the list: the two panes are one pair.
+        // 3. The detail pane's plate. Same fill and same radius as the list:
+        // the two panes are one pair, and the gap between them is the seam —
+        // there is no drawn separator line. The split is still draggable in
+        // that gap; `cursor_icon` puts resize arrows over the grab band, which
+        // is what advertises it now that nothing is painted there.
         // Nothing here reaches the plate's corners (the body carries its own
         // text bounds), so this needs no rounded clip the way the list — whose
         // cards span its full width — does.
@@ -4766,7 +4769,6 @@ impl Application for ClearEmailApp {
                 cce_ui::color::list_bg_color(),
             );
         }
-        quads.push((separator_x, MENUBAR_H, 1.0, h_f32 - MENUBAR_H, [0.18, 0.18, 0.22, 1.0]));
 
         // Search band (only while open) and the list
         if self.search_open {
@@ -5085,9 +5087,10 @@ impl Application for ClearEmailApp {
     }
 
     fn cursor_icon(&self, x: f32, y: f32) -> Option<CursorIcon> {
-        // Resize arrows over the split separator's grab band, and for the
-        // whole drag — mid-drag the pointer legally outruns the clamped
-        // line, and the cursor must not flicker back to the arrow there.
+        // Resize arrows over the split's grab band — the only thing marking
+        // the split now that the separator line is gone — and for the whole
+        // drag: mid-drag the pointer legally outruns the clamped split, and
+        // the cursor must not flicker back to the arrow there.
         if !self.compose_open
             && !cce_ui::widget::context_menu::is_visible()
             && (self.split_dragging