Snap animated paths to MyGo's path-cache grid; removes cross-test snapshot flake

AGENTS.md

@@ -37,6 +37,7 @@ testdata/snapshots/  <os>/<name>-<light|dark>.png
 - Focus: `internal.Ring(e, k.Focus, radius)` for the 2 DIP ring with 2 DIP gap.
 - State marks (checked, selected, progress) use `OnAccent` on `Accent`, or `AccentText`, never `Accent` alone on dark surfaces (2.44:1).
 - Ornament color only for dividers, corners, panel titles. No gradients, glow, glass or texture.
+- Animated paths: pass coordinates through `internal.Snap(p, v)`. MyGo caches path masks by quarter-pixel keys (ui/path.go); unsnapped motion reuses near-miss masks and breaks snapshots.
 - Durations: `mujica.Motion(c, theme.StateDuration)`; popups use `theme.PopupDuration`.
 - Disabled blocks input before handling it (`Disabled(true)`); MyGo dims disabled elements, do not add opacity.
 - Copy shown by a component comes from `msg(c, key)`; business copy comes from the caller.

internal/paint.go

@@ -2,6 +2,8 @@
 package internal
 
 import (
+	"math"
+
 	"github.com/egoist/mygo/ui"
 
 	"mujicaui/theme"
@@ -33,3 +35,9 @@ func Diamond(cx, cy, s float32) *ui.Path {
 	p.Close()
 	return &p
 }
+
+// Snap rounds v to MyGo's quarter-device-pixel path cache grid.
+func Snap(p *ui.Painter, v float32) float32 {
+	g := 4 * p.Scale()
+	return float32(math.Round(float64(v*g))) / g
+}

spinner.go

@@ -48,7 +48,7 @@ func Spinner(c *ui.Context, opts SpinnerOptions) *ui.Element {
 				x := cx + rad*float32(math.Cos(a))
 				y := cy + rad*float32(math.Sin(a))
 				alpha := 1 - float32(i)*0.22
-				p.FillPath(internal.Diamond(x, y, r.W*0.3), color.Alpha(alpha))
+				p.FillPath(internal.Diamond(internal.Snap(p, x), internal.Snap(p, y), internal.Snap(p, r.W*0.3)), color.Alpha(alpha))
 			}
 		})
 		if opts.ShowLabel {