render: flat stroke replaces the scene viewer's relief lip

The Boss rim's SDF band contours pull inside the true superellipse at
window-scale radii, so the lit lip visibly cut the corner against the
compositor's silhouette clip (overlaying the analytic arc on the buffer
shows the band sagging inward at the diagonal while hugging the edges),
and its shadow side re-tinted whatever scene color it crossed. The lip
is now the plated panes' flat-border degradation: a tessellated
plate_border stroke on the full-window rect, following the exact
window arc. Focus colors the stroke with the highlight under
control_relief; with relief off append_context_border owns the ring,
as for every pane.

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

 src/render.rs | 42 +++++++++++++++++++++---------------------
 1 file changed, 21 insertions(+), 21 deletions(-)

diff --git a/src/render.rs b/src/render.rs
index 90b857b..fb06818 100644
--- a/src/render.rs
+++ b/src/render.rs
@@ -247,32 +247,32 @@ impl State {
             append_widget_plate_radii(w, pc, None, self.pane_plate_radii(wx, wy, ww2, wh2));
             w.paint_self(&self.ui_context, pc);
         } else if idx == VIEWPORT_IDX {
-            // The viewport wears the plate bevel's rim only. It can't be a real
-            // `Bevel` plate: the SDF plate draw owns fill AND roll together, so a
-            // transparent fill kills the roll and the params fill would frost the
-            // whole 3D scene behind its blur marker. A `Boss` step is the rim
-            // alone — a fill-less overlay of translucent light/shadow over the
-            // scene. Same gate as the plated panes (plate border + control_relief)
-            // so the DE style flips together. The rim spans the WHOLE window,
-            // not the viewport column: the 3D canvas is full-bleed (CANVAS_IDX
-            // covers the window and the other panes float over it), so the
-            // scene viewer's relief is the window's own backplate edge — full
-            // rect, window radius on all four corners, concentric with the
-            // compositor's silhouette clip. A column-rect rim floated arcs in
-            // the middle of the scene that read as wrong-radius corners.
-            if cce_ui::layout::control_relief() && cce_ui::colors::plate_border_color().is_some() {
+            // The scene viewer's lip is a FLAT stroke on the window arc, not a
+            // relief. A Boss rim was tried twice and rejected: the SDF relief
+            // band's contours pull inside the true superellipse at window-scale
+            // radii, so the lit lip visibly cut the corner against the
+            // compositor's silhouette clip, and its shadow side re-tinted the
+            // scene it crossed. The tessellated border stroke follows the exact
+            // arc. It spans the WHOLE window, not the viewport column: the 3D
+            // canvas is full-bleed (CANVAS_IDX covers the window; the other
+            // panes float over it), so this lip is the window's own backplate
+            // edge — window radius on all four corners, concentric with the
+            // silhouette. Focus marks by coloring the stroke with the highlight
+            // (standing in for the plated panes' bevel tint); with
+            // control_relief off, append_context_border owns the focus ring as
+            // for every pane.
+            if let Some(bc) = cce_ui::colors::plate_border_color() {
                 let (px, py, pw, ph) = (0.0, 0.0, self.width, self.height);
                 if pw > 0.0 && ph > 0.0 {
                     let vp_rect = rect(px, py, pw, ph);
                     let radii = self.pane_plate_radii(px, py, pw, ph);
-                    let depth = cce_ui::colors::plate_bevel_width();
-                    // Focus marks through the rim's specular tint, exactly the
-                    // plated panes' treatment (plate_focus_tint).
-                    if let Some(tint) = self.plate_focus_tint(idx) {
-                        pc.boss_edges_tinted(vp_rect, radii, depth, (true, true, true, true), tint);
+                    let color = if cce_ui::layout::control_relief() && self.focused_pane == RIGHT_MENUBAR_IDX {
+                        let hl = colors::highlight_primary_color();
+                        [hl[0], hl[1], hl[2], 0.9]
                     } else {
-                        pc.boss_edges(vp_rect, radii, depth, (true, true, true, true));
-                    }
+                        bc
+                    };
+                    pc.border(vp_rect, radii, [0.0; 4], color, cce_ui::colors::plate_border_thickness());
                 }
             }
             for (qx, qy, qw, qh, qc) in w.extra_quads() {