Wire up decode puzzle chain and lock terminal on file removal

Connects the previously-disconnected /decode command to per-player
messages: player 1 unlocks sudo for everyone, player 2 unlocks a scan
command that reveals which files the AI virus has locked, player 3
learns those files should be removed.

Also adds a retaliation mechanic: successfully removing a file locks
the player's terminal. The AI virus locks it out in red immediately;
the mainframe reveals a 12-character recovery code in green after 30
seconds, which can be submitted via /unlock to restore access early,
otherwise the terminal auto-recovers after 45 seconds.

assets/styles/game1.css

@@ -55,6 +55,48 @@ div.message {
     white-space: pre-wrap;
 }
 
+div.message-virus {
+    color: #F00;
+    font-weight: bold;
+}
+
+div.message-mainframe {
+    color: #0F0;
+}
+
+div#lock-banner {
+    position: fixed;
+    top: 68px;
+    left: 0;
+    width: 100%;
+    padding: 12px 20px;
+    background-color: #200;
+    border-top: 1px solid #F00;
+    border-bottom: 1px solid #F00;
+    color: #F00;
+    font-size: 18px;
+    font-weight: bold;
+    letter-spacing: 1px;
+    z-index: 99;
+    display: flex;
+    justify-content: space-between;
+    align-items: center;
+    animation: lock-banner-pulse 1s ease-in-out infinite;
+}
+
+@keyframes lock-banner-pulse {
+    0%, 100% {
+        background-color: #200;
+    }
+    50% {
+        background-color: #400;
+    }
+}
+
+body.locked div#message-container {
+    padding-top: 130px;
+}
+
 div#input {
     padding: 20px;
 }