fix(web): symmetric decode-tab triangle (Decode prefix arrow in, decode arrow out)

Author: pmarreck

index.html

@@ -154,7 +154,7 @@ <h1>PrintableBinary Encoder/Decoder</h1>
       <p class="subtitle">Encode binary files into human-readable UTF-8 text — and decode them back</p>
       <div class="tabs" role="tablist">
         <button class="tab active" id="tabEncode" data-mode="encode" role="tab">▶ Encode</button>
-        <button class="tab" id="tabDecode" data-mode="decode" role="tab">Decode</button>
+        <button class="tab" id="tabDecode" data-mode="decode" role="tab">Decode ▶</button>
       </div>
     </header>