Constrain skill-cta width to match the steps (880px)

The 'Hand the setup to your agent' box had no max-width and stretched to the full body width (~1140px), while the steps below it cap at 880px. Match them. (Was lost from the previous PR — merged before this commit landed.)

index.html

@@ -146,7 +146,7 @@
   .skill-cta {
     display: flex; align-items: center; gap: 16px; flex-wrap: wrap;
     background: var(--accent-soft); border: 1px solid #c3d2ec; border-radius: 4px;
-    padding: 14px 16px; margin: 20px 0 6px;
+    padding: 14px 16px; margin: 20px 0 6px; max-width: 880px;
   }
   .skill-cta .txt { font-size: 12.5px; color: var(--ink-2); line-height: 1.5; flex: 1; min-width: 220px; }
   .skill-cta .txt b { font-weight: 600; }