feat(desktop): add computeWebviewBounds helper

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

desktop/src/components/browser/computeWebviewBounds.test.ts

@@ -0,0 +1,14 @@
+import { describe, expect, it } from 'vitest'
+import { computeWebviewBounds } from './computeWebviewBounds'
+
+describe('computeWebviewBounds', () => {
+  it('maps a DOMRect to logical bounds (rounded)', () => {
+    const rect = { left: 100.4, top: 50.6, width: 800.2, height: 600.9 } as DOMRect
+    expect(computeWebviewBounds(rect)).toEqual({ x: 100, y: 51, width: 800, height: 601 })
+  })
+
+  it('clamps negative/zero sizes to 0', () => {
+    const rect = { left: -5, top: -5, width: -10, height: 0 } as DOMRect
+    expect(computeWebviewBounds(rect)).toEqual({ x: -5, y: -5, width: 0, height: 0 })
+  })
+})

desktop/src/components/browser/computeWebviewBounds.ts

@@ -0,0 +1,10 @@
+export type WebviewBounds = { x: number; y: number; width: number; height: number }
+
+export function computeWebviewBounds(rect: Pick<DOMRect, 'left' | 'top' | 'width' | 'height'>): WebviewBounds {
+  return {
+    x: Math.round(rect.left),
+    y: Math.round(rect.top),
+    width: Math.max(0, Math.round(rect.width)),
+    height: Math.max(0, Math.round(rect.height)),
+  }
+}