Spacing: the window-edge inset is the roll plus the padding

The inset from the window edge read root_plate_padding(), a run of flat
face that on a rolled root plate begins only where the roll ends; it is
now layout::root_plate_inset(), the ladder's one number for that edge
(bevel_width plus the padding), so the flat run at the rim matches the
gap between siblings on the plate.

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

 src/main.rs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/main.rs b/src/main.rs
index 92d6c78..2763d0f 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -92,7 +92,8 @@ fn text_leaf_height(font_size: f32) -> f32 {
 }
 
 fn metrics(width: f32) -> Metrics {
-    let pad = cce_ui::layout::root_plate_padding();
+    // The window-edge inset: the root plate's roll plus one padding.
+    let pad = cce_ui::layout::root_plate_inset();
     let band_h = pad + text_leaf_height(TITLE_FONT_SIZE) + 10.0;
     let gap = cce_ui::layout::bevel_width().max(4.0);
     let input_y = band_h + gap;