integration: name case metrics, split delivered offerings from offers, and frame the stack honestly

Give every metrics list a localized heading, keep delivered Rösterei tools out of the offer boundary, and describe the skills grid as a familiarity overview with an evidence note instead of claiming public-case backing for every item.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/app/shared/case-study/case-study.html

@@ -36,7 +36,10 @@
   </section>
 
   @if (caseStudy().metrics.length > 0) {
-    <app-metric-list [metrics]="caseStudy().metrics" [labelledBy]="metricsLabelId()" />
+    <section class="stack" [attr.aria-labelledby]="metricsLabelId()">
+      <h3 [id]="metricsLabelId()">{{ metricsLabel() }}</h3>
+      <app-metric-list [metrics]="caseStudy().metrics" [labelledBy]="metricsLabelId()" />
+    </section>
   }
 
   <section class="stack" [attr.aria-labelledby]="caseStudy().id + '-stack'">