docs: remove Redis slide from presentation deck

docs/presentation/index.html

@@ -254,8 +254,7 @@
     <div class="tabs">
       <button class="tab active" data-section="1"><span class="tab-num">1</span>Problem</button>
       <button class="tab" data-section="2"><span class="tab-num">2</span>Architecture</button>
-      <button class="tab" data-section="3"><span class="tab-num">3</span>Redis</button>
-      <button class="tab" data-section="4"><span class="tab-num">4</span>Experiments</button>
+      <button class="tab" data-section="4"><span class="tab-num">3</span>Experiments</button>
     </div>
   </div>
 </nav>
@@ -360,38 +359,6 @@ <h3>Worker ↔ Worker</h3>
 </section>
 
 <!-- ═════════════════════════════════════════════════════════
-     3 · REDIS + COORDINATION
-═══════════════════════════════════════════════════════════ -->
-<section class="section" id="s3">
-  <div class="kicker">03 · Coordination</div>
-  <h1>Redis is the nervous system.</h1>
-  <p class="tagline">Five roles. One server. Single-writer orchestrator. No locks.</p>
-
-  <div class="redis-hub">
-    <div class="center">
-      <div class="t">ElastiCache · cache.t3.micro</div>
-      <div class="n">Redis 7</div>
-    </div>
-    <div class="redis-roles">
-      <div class="rrole"><div class="role-n">Broker</div><div class="role-k">celery · db=1</div></div>
-      <div class="rrole"><div class="role-n">State</div><div class="role-k">run:{id}:*</div></div>
-      <div class="rrole"><div class="role-n">Stream</div><div class="role-k">sse:{id}</div></div>
-      <div class="rrole"><div class="role-n">Semaphore</div><div class="role-k">≤29 in-flight</div></div>
-      <div class="rrole"><div class="role-n">Cache</div><div class="role-k">SETNX idempotency</div></div>
-    </div>
-  </div>
-
-  <h2>The counter pattern (distributed barrier)</h2>
-  <div class="oneline">
-    <code>INCR</code> is atomic. 100 concurrent workers → unique sequence numbers.<br/>
-    At 95%, <code>SETNX</code> guards the transition — <span class="acc">exactly once</span>, even under races.
-  </div>
-
-  <h2>Stream, not pub/sub</h2>
-  <div class="oneline">
-    Streams persist, support cursors, replay. Reconnect mid-run → <code>Last-Event-ID</code> resumes from exactly that cursor. <span class="acc eval">Multi-tab safe, zero extra code.</span>
-  </div>
-</section>
 
 <!-- ═════════════════════════════════════════════════════════
      4 · EXPERIMENTS
@@ -600,8 +567,8 @@ <h2 style="margin-top: 40px;">M5 + M6 — Supporting experiments</h2>
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+    else if (e.key === 'ArrowRight' && current < 3) { show([1,2,4][current]); }
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