feat: add quantum Markov chain card to complete grid, strip domain references from how-it-works

Author: dcoldeira

index.html

@@ -1002,6 +1002,12 @@ <h2>What people ask Bell</h2>
           <div class="example-q">"Can a quantum switch with indefinite causal order transmit information through two completely depolarising channels?"</div>
           <div class="example-a">Fixed order: capacity = <strong>0 bits/use</strong> (both channels fully depolarising). Quantum switch: capacity &gt; 0 — indefinite causal order activates a classically forbidden channel.</div>
         </div>
+
+        <div class="example-card">
+          <div class="example-domain">Quantum Markov chains</div>
+          <div class="example-q">"In a quantum network Alice → Bob → Charlie, is Charlie conditionally independent of Alice given Bob?"</div>
+          <div class="example-a">Quantum conditional mutual information I(A:C|B) = <strong>0.000 bits</strong>. Markov condition holds — Charlie's state depends on Alice only through Bob. Quantum data processing inequality satisfied.</div>
+        </div>
       </div>
     </div>
   </section>
@@ -1017,7 +1023,7 @@ <h2>From question to physics in seconds</h2>
         <div class="step">
           <div class="step-num">1</div>
           <h3>Ask in plain English</h3>
-          <p>Describe your quantum problem naturally. Bell understands quantum networks, entanglement, causal structures, photonic hardware, quantum biology, quantum sensing, and quantum chemistry.</p>
+          <p>Describe your quantum problem naturally. Bell understands quantum correlations, entanglement, causal structure, quantum channels, and photonic networks.</p>
         </div>
         <div class="step">
           <div class="step-num">2</div>