docs: add ECL Reference and Workbench screenshots to website

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: dionmcm

docs/index.html

@@ -114,6 +114,22 @@ <h2>Write, test, and refine ECL expressions</h2>
 
   <hr class="feature-divider">
 
+  <!-- ECL Reference -->
+  <section class="feature stacked">
+    <div class="feature-text">
+      <div class="label">ECL Reference</div>
+      <h2>Built-in ECL documentation at your fingertips</h2>
+      <p>Fifty searchable articles covering every ECL operator, refinement, filter, pattern, and history supplement —
+        with syntax explanations, examples, and tables. No need to leave the app or search the specification.
+        Stays visible alongside your work so you can look up syntax while writing expressions.</p>
+    </div>
+    <div class="feature-image">
+      <img src="screenshot-ecl-reference.png" alt="ECL Reference panel with searchable knowledge articles">
+    </div>
+  </section>
+
+  <hr class="feature-divider">
+
   <!-- Visualise -->
   <section class="feature stacked">
     <div class="feature-text">