fix(cli): consolidate layout and contrast audit correctness (#2401)

* fix(cli): respect transparent image pixels in occlusion audit

* test(cli): cover contained image letterboxing

* fix(cli): account for text strokes in contrast checks

* fix(cli): honor text overflow opt-outs

* fix(cli): skip contrast on transparent backdrops

* chore(skills): refresh generated manifest

packages/cli/src/utils/checkBrowser.ts

@@ -510,7 +510,11 @@ async function collectContrast(
     // This screenshot is the one contrast math is sampled from below — it must
     // stay untouched by the annotation overlay (finishContrast reads real
     // painted pixels), so annotation only ever happens on a SECOND shot.
-    const measurementShot = await page.screenshot({ encoding: "base64", type: "png" });
+    const measurementShot = await page.screenshot({
+      encoding: "base64",
+      type: "png",
+      omitBackground: true,
+    });
     if (typeof measurementShot !== "string") throw new Error("Contrast screenshot was not base64");
     const raw = await finishContrast(
       page,