refactor(ComparisonView): extract strut-height and settled-text from Line

Pull the baseline-strut height math into a documented computeStrutHeight
util (named constants for the empirical 0.34 / 1.1 factors, with a unit
test) and the per-side native text runs into a SettledText component.
Strut statics move to Tailwind classes with only the height as style:height;
drop the now-redundant style-string $derived bindings.

src/widgets/ComparisonView/lib/utils/computeStrutHeight/computeStrutHeight.test.ts

@@ -0,0 +1,28 @@
+import {
+    describe,
+    expect,
+    it,
+} from 'vitest';
+import { computeStrutHeight } from './computeStrutHeight';
+
+describe('computeStrutHeight', () => {
+    it('uses the centering height when the line-height is generous', () => {
+        // centering = 40/2 + 16*0.34 = 25.44; floor = 16*1.1 = 17.6 → centering wins.
+        expect(computeStrutHeight(40, 16)).toBeCloseTo(25.44, 5);
+    });
+
+    it('falls back to the ascent floor when the line-height is tight', () => {
+        // centering = 16/2 + 16*0.34 = 13.44; floor = 16*1.1 = 17.6 → floor wins.
+        expect(computeStrutHeight(16, 16)).toBeCloseTo(17.6, 5);
+    });
+
+    it('treats the floor and centering height as equal at the crossover line-height', () => {
+        // centering == floor when lineHeight = 1.52 * fontSize → 24.32 for 16px.
+        expect(computeStrutHeight(24.32, 16)).toBeCloseTo(17.6, 5);
+    });
+
+    it('scales with font size', () => {
+        // centering = 60/2 + 32*0.34 = 40.88; floor = 32*1.1 = 35.2 → centering wins.
+        expect(computeStrutHeight(60, 32)).toBeCloseTo(40.88, 5);
+    });
+});