fix(cli): contrast gate judges only readable content; examples pass check

Three filters keep the escalated contrast gate honest, each surfaced by
running check across the registry examples:
- data-layout-ignore (the layout audit's existing decorative opt-out)
  now also excludes set-dressing text from the contrast audit — one
  vocabulary for 'not copy a viewer must read'.
- Text that has (nearly) left the canvas is skipped: sampling a clamped
  off-canvas box reads border pixels and produced the classic false
  white-on-white (a cursor exiting the frame).
- Contrast failures follow the same persistence rule as layout findings:
  observed at a single sample of a multi-sample sweep demotes to
  warning; held failures gate.

Example fixes the sweep exposed: motion-blur's 21 deliberately-dim rail
labels are marked decorative (its vivid labels pass on their own);
nyt-graph's subtitle and source-note adopt the gate's suggested
compliant gray; decision-tree's declared duration drops 15s to 10s —
its content ends at ~9.5s and every render shipped a blank white tail.

packages/cli/src/commands/contrast-audit.browser.js

@@ -158,6 +158,22 @@ window.__contrastAuditPrepare = function () {
     }
     if (!hasText) continue;
 
+    // Same decorative opt-out the layout audit honors: text marked (or inside)
+    // data-layout-ignore is set dressing, not copy a viewer must read —
+    // deliberately dim rail labels, ghost typography, texture text.
+    if (el.closest && el.closest("[data-layout-ignore]")) continue;
+
+    // Text that has (nearly) left the canvas — a cursor exiting the frame, an
+    // element parked off-screen — is not readable content, and sampling its
+    // clamped edge reads whatever pixels happen to sit at the border (the
+    // classic false "white-on-white"). Require a minimally-visible on-canvas
+    // intersection before judging contrast; the layout audit separately owns
+    // off-canvas detection as its own finding class.
+    var vis = el.getBoundingClientRect();
+    var onX = Math.min(vis.right, window.innerWidth) - Math.max(vis.left, 0);
+    var onY = Math.min(vis.bottom, window.innerHeight) - Math.max(vis.top, 0);
+    if (onX < 8 || onY < 8) continue;
+
     var cs = getComputedStyle(el);
     if (cs.visibility === "hidden" || cs.display === "none") continue;
     if (parseFloat(cs.opacity) <= 0.01) continue;