toggle, widget: scale the pill with an explicit row height, and give elide a half-pixel tolerance

Toggle::height used to adjust only the row: the resolved value was floored at the theme track height and the pill kept its theme size, so a toggle capped below the fluid row height still rendered a full-size pill — on large surfaces, visibly out of scale next to controls that honour their cap. The floor is gone; when the resolved height falls below the theme row height, track and thumb now scale down proportionally (never up — the factor is capped at 1), and preferred_size reports the scaled track width so layout, focus ring and centring stay consistent. A toggle without an explicit height is untouched.
elide compared measure( text ) <= max_w strictly, which breaks when the caller sized itself from the same measurement: a button reports text + 2×pad as its preferred width, the layout grants exactly that, and draw hands elide back rect.width − 2×pad. In f32 the add-then-subtract round-trip can land a few ULP under the original measurement, the strict comparison fails, and the truncation branch then costs the full width of the ellipsis — a sub-pixel deficit turned "Empezar" into "Empez...". The fit check now allows half a pixel of slack, which absorbs any mismatch of this class while leaving genuine overflows to truncate as before.

src/widget/mod.rs

@@ -128,7 +128,10 @@ pub( crate ) fn elide(
 	{
 		return String::new();
 	}
-	if canvas.measure_text( text, size ) <= max_w
+	// Half-pixel slack: a parent that sized itself from this same
+	// measurement can hand back a width a few ULP short after its
+	// padding add-then-subtract round-trip.
+	if canvas.measure_text( text, size ) <= max_w + 0.5
 	{
 		return text.to_string();
 	}