Refactor: one colorFade transition replaces internal.Fade

textInputFade becomes colorFade in theme.go and serves AvatarGroup,
Image retry, Tag and EditableText, which used internal.Fade. MyGo already
skips element transitions under ReduceMotion, so dropping the Motion
check keeps behaviour.

internal/display.go

@@ -2,19 +2,10 @@ package internal
 
 import (
 	"math"
-	"time"
 
 	"github.com/egoist/mygo/ui"
 )
 
-// Fade animates e's colors over d; zero skips it.
-func Fade(e *ui.Element, d time.Duration) *ui.Element {
-	if d > 0 {
-		e.Transition(ui.ElementTransition{Colors: true, Duration: d})
-	}
-	return e
-}
-
 // Rule draws a pixel-aligned 1 DIP horizontal line at y.
 func Rule(p *ui.Painter, x0, x1, y float32, c ui.Color) {
 	yy := ruleY(p, y)