fix: the params pane's hover wash is painted after its carves, not before

Hovering any row re-lit every well in the pane. The wash is ordinary
geometry, and the tessellator ends a plate's carve-grouping window at the
first ordinary geometry painted after it — so with the wash emitted
before the wells, every recess in the pane lost the pane plate as its
host and shaded through the overlay fallback instead of the plate's own
draw. The two shadings differ visibly (a crisp shade line against a soft
lit crest), which read as all the wells brightening on hover; the
dropdowns, which carve nothing, were the only rows that held still.
Measured in a shadow session with the user's project on both GPUs, and
diagnosed from the tessellation's own comment on what closes a window.

The wash now follows the fillets, after every recess, boss, trough and
groove the pane emits; `the_hover_wash_comes_after_every_carve` pins
the order in the emitted display list.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

 src/widget/container/parameters_bg.rs | 43 ++++++++++++++++++++++++++++++++---
 1 file changed, 40 insertions(+), 3 deletions(-)

diff --git a/src/widget/container/parameters_bg.rs b/src/widget/container/parameters_bg.rs
index 931a60d..2ddbddf 100644
--- a/src/widget/container/parameters_bg.rs
+++ b/src/widget/container/parameters_bg.rs
@@ -864,8 +864,9 @@ impl ParametersBg {
         })
     }
 
-    /// The hovered row's tint, over its floor and under its control: the
-    /// dialog's hover-row wash, at the control corner radius.
+    /// The hovered row's tint: the dialog's hover-row wash, at the control
+    /// corner radius, laid over the row's carves (see `paint_ui` for why it
+    /// must come after them).
     fn paint_hover_row(&self, ctx: &mut PaintCtx) {
         let Some(i) = self.hover_row else { return };
         let Some(&(x, y, w, h)) = self.get_param_rects().get(i) else { return };
@@ -1884,7 +1885,6 @@ impl Paint for ParametersBg {
             return;
         }
         self.paint_row_floors(ctx);
-        self.paint_hover_row(ctx);
         for (qx, qy, qw, qh, qr, qc, corners) in self.rounded_quads(ui) {
             ctx.rounded_rect(Rect { x: qx, y: qy, width: qw, height: qh }, qr, corners, qc);
         }
@@ -1907,6 +1907,16 @@ impl Paint for ParametersBg {
         for (fcx, fcy, fr, fd, fs) in self.section_fillets() {
             ctx.concave_fillet(fcx, fcy, fr, fd, fs, false);
         }
+        // AFTER every carve, never before: the wash is ordinary geometry,
+        // and ordinary geometry painted after the pane plate ends its
+        // carve-grouping window (`window_runner`'s tessellation) — every
+        // recess emitted after it loses the plate as its host and shades
+        // through the overlay fallback instead of the plate's own draw. For
+        // the day it sat above the carves (2026-09-28) hovering ANY row
+        // re-lit every well in the pane: the grouped and fallback shadings
+        // differ visibly (a crisp shade line against a soft lit crest), and
+        // the flip read as "all the wells brighten on hover".
+        self.paint_hover_row(ctx);
         for (scx, scy, sr, sc) in self.spheres() {
             ctx.sphere(scx, scy, sr, &crate::scene::material::Material::from_fill(sc));
         }
@@ -4098,6 +4108,33 @@ mod tests {
         assert_eq!(p.hover_row, None);
     }
 
+    /// The hover wash is painted after every carve in the pane. Ordinary
+    /// geometry ends the pane plate's carve-grouping window, so a wash
+    /// emitted BEFORE the wells would drop every one of them to the overlay
+    /// shading — which is what happened for a day, and read as every well
+    /// re-lighting whenever any row was hovered.
+    #[test]
+    fn the_hover_wash_comes_after_every_carve() {
+        use crate::scene::paint::Prim;
+        let mut ctx = UiContext::new();
+        let mut p = panel_with(&[("Name", "x", "text"), ("Count", "3", "spinbox:0:10"), ("Size", "0.5", "slider:0:1")]);
+        WidgetHost::set_rect(&mut p, 0.0, 0.0, 300.0, 400.0);
+        let (x, y, w, h) = p.get_param_rects()[1];
+        p.on_cursor_moved(x + w * 0.5, y + h * 0.5, &mut ctx);
+        assert_eq!(p.hover_row, Some(1));
+
+        let mut pc = crate::scene::paint::PaintCtx::new();
+        Paint::paint_ui(&*p, &ctx, Rect { x: 0.0, y: 0.0, width: 300.0, height: 400.0 }, &mut pc);
+        let items = pc.finish().items;
+        let is_carve = |prim: &Prim| matches!(prim, Prim::Recess { .. } | Prim::Boss { .. } | Prim::Trough { .. } | Prim::Ridge { .. });
+        let last_carve = items.iter().rposition(|i| is_carve(&i.prim)).expect("the rows carve at least one well");
+        let wash = items
+            .iter()
+            .position(|i| matches!(&i.prim, Prim::RoundedRect { color, .. } if *color == [1.0, 1.0, 1.0, 0.05]))
+            .expect("the hovered row's wash is painted");
+        assert!(wash > last_carve, "wash at {wash} must follow the last carve at {last_carve}");
+    }
+
     /// The row tint is the pane's rule, not the control's: a spinbox row,
     /// which draws no hover of its own under the relief style, is tinted
     /// exactly as a slider row is, and a section header never is.