Fix: add missing HTML IDs causing JS crash in pages 1, 3, 5

Root cause: <table> elements used class='truth-table'/'state-table' but JS
referenced getElementById('truth-table')/'state-table') — returned null,
crashed renderAll() before canvas animation or language event listeners
could initialize.

Fixes:
- page1: added id='truth-table' to truth table element
- page3: added id='state-table' to state table element
- page5: added background to brain-region divs for visibility
- All 6 pages verified: zero JS↔HTML ID mismatches, valid syntax

Co-Authored-By: Claude <noreply@anthropic.com>

Author: KIRRAWA

page1-logic-gates.html

@@ -123,7 +123,7 @@ <h2><span class="dot"></span> <span id="left-title">Logic Gate</span></h2>
         <span id="output-text" style="font-size:13px;color:var(--text-dim)">0</span>
       </div>
     </div>
-    <table class="truth-table"><thead></thead><tbody></tbody></table>
+    <table class="truth-table" id="truth-table"><thead></thead><tbody></tbody></table>
   </section>
 
   <section class="panel">

page3-state-machines.html

@@ -76,7 +76,7 @@ <h2><span class="dot"></span> <span id="left-title">Sequential Logic — Flip-Fl
       <button class="ff-btn" data-ff="JK">JK Flip-Flop</button>
     </div>
     <div id="ff-diagram" style="display:flex;flex-direction:column;align-items:center;gap:14px;padding:8px 0"></div>
-    <table class="state-table"><thead></thead><tbody></tbody></table>
+    <table class="state-table" id="state-table"><thead></thead><tbody></tbody></table>
   </section>
 
   <section class="panel">

page5-von-neumann.html

@@ -36,7 +36,7 @@
   .bus-bar{flex:1;height:2px;background:var(--border);border-radius:1px}
   .bus-label{font-size:9px;color:var(--text-dim)}
   .brain-layout{position:relative;width:100%;height:390px}
-  .brain-region{position:absolute;border:2px solid var(--border);border-radius:8px;padding:9px 12px;cursor:pointer;transition:all .3s;font-size:10px}
+  .brain-region{position:absolute;border:2px solid var(--border);border-radius:8px;padding:9px 12px;cursor:pointer;transition:all .3s;font-size:10px;background:rgba(20,20,30,0.85)}
   .brain-region:hover{border-color:var(--accent)}
   .brain-region.highlight{border-color:var(--accent);box-shadow:0 0 16px var(--accent-glow);background:rgba(78,201,176,0.08)}
   .brain-region .rname{color:#ddd;font-weight:600;font-size:11px}