docs: add ECL Workbench to website landing page

Add feature section with screenshot, update hotkey grid from 5 to 6.

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

Author: dionmcm

docs/index.html

@@ -97,6 +97,23 @@ <h2>Make ECL expressions readable</h2>
 
   <hr class="feature-divider">
 
+  <!-- ECL Workbench -->
+  <section class="feature stacked">
+    <div class="feature-text">
+      <div class="label">ECL Workbench</div>
+      <h2>Write, test, and refine ECL expressions</h2>
+      <p>A full ECL editor with syntax highlighting, autocomplete, inline diagnostics, and code actions — powered by
+        Monaco. Write an expression, see matching concepts instantly. Hover over concept IDs for details, use
+        quick fixes to add history supplements or description filters, and toggle display terms with a keystroke.
+        Open concept diagrams or browse them in Shrimp, right from the results.</p>
+    </div>
+    <div class="feature-image">
+      <img src="screenshot-ecl-workbench.png" alt="ECL Workbench with Monaco editor and evaluation results">
+    </div>
+  </section>
+
+  <hr class="feature-divider">
+
   <!-- Visualise -->
   <section class="feature stacked">
     <div class="feature-text">
@@ -113,7 +130,7 @@ <h2>See concept relationships at a glance</h2>
 
   <!-- Hotkeys -->
   <section class="hotkeys">
-    <h2>Five hotkeys. Zero friction.</h2>
+    <h2>Six hotkeys. Zero friction.</h2>
     <p class="subtitle">Works from any app — no switching windows, no browser tabs.</p>
     <div class="hotkey-grid">
       <div class="hotkey-card">
@@ -132,6 +149,10 @@ <h2>Five hotkeys. Zero friction.</h2>
         <div class="keys">⌃⌥E</div>
         <div class="action">ECL Format</div>
       </div>
+      <div class="hotkey-card">
+        <div class="keys">⌃⌥V</div>
+        <div class="action">ECL Workbench</div>
+      </div>
       <div class="hotkey-card">
         <div class="keys">⌃⌥H</div>
         <div class="action">Shrimp</div>