fix: [A11Y] Add labels/tooltips for top-right icon controls (closes #703)

- Add aria-label to all top-right controls (Atlas button, Bannerlord status, Agent Thought Stream)
- Add role attributes (status, log) for screen reader semantics
- Add aria-live for dynamic content (Agent Thought Stream)
- Add aria-hidden to decorative icons (emoji icons, status dots)
- Add aria-label to all CLOSE buttons across overlays (vision, portal, memory, session room, atlas)
- Add CSS tooltip system using data-tooltip attributes
- Tooltips appear on hover and keyboard focus (focus-visible)
- Add focus-visible keyboard navigation ring for all interactive controls
- Add aria-label to controls hint and Hermes status indicator
- Mark decorative elements with aria-hidden

First-time users can now infer what each control does via hover tooltips and keyboard focus.

index.html

@@ -113,15 +113,15 @@
 
   <!-- Top Right: Agent Log & Atlas Toggle -->
   <div class="hud-top-right">
-    <button id="atlas-toggle-btn" class="hud-icon-btn" title="Portal Atlas">
-      <span class="hud-icon">🌐</span>
+    <button id="atlas-toggle-btn" class="hud-icon-btn" aria-label="Open Portal Atlas — browse all available portals" title="Open Portal Atlas" data-tooltip="Portal Atlas (M)">
+      <span class="hud-icon" aria-hidden="true">🌐</span>
       <span class="hud-btn-label">ATLAS</span>
     </button>
-    <div id="bannerlord-status" class="hud-status-item" title="Bannerlord Readiness">
-      <span class="status-dot"></span>
+    <div id="bannerlord-status" class="hud-status-item" role="status" aria-label="Bannerlord system readiness indicator" title="Bannerlord Readiness" data-tooltip="Bannerlord Status">
+      <span class="status-dot" aria-hidden="true"></span>
       <span class="status-label">BANNERLORD</span>
     </div>
-    <div class="hud-agent-log" id="hud-agent-log" aria-label="Agent Thought Stream">
+    <div class="hud-agent-log" id="hud-agent-log" role="log" aria-label="Agent Thought Stream — live activity feed" aria-live="polite">
       <div class="agent-log-header">AGENT THOUGHT STREAM</div>
       <div id="agent-log-content" class="agent-log-content"></div>
     </div>
@@ -155,11 +155,11 @@
   </div>
 
   <!-- Controls hint + nav mode -->
-  <div class="hud-controls">
+  <div class="hud-controls" aria-label="Keyboard and mouse controls">
     <span>WASD</span> move &nbsp; <span>Mouse</span> look &nbsp; <span>Enter</span> chat &nbsp;
     <span>V</span> mode: <span id="nav-mode-label">WALK</span>
     <span id="nav-mode-hint" class="nav-mode-hint"></span>
-    &nbsp; <span class="ws-hud-status">HERMES: <span id="ws-status-dot" class="chat-status-dot"></span></span>
+    &nbsp; <span class="ws-hud-status">HERMES: <span id="ws-status-dot" class="chat-status-dot" role="status" aria-label="Hermes WebSocket connection status"></span></span>
   </div>
 
   <!-- Portal Hint -->
@@ -183,7 +183,7 @@
       </div>
       <h2 id="vision-title-display">SOVEREIGNTY</h2>
       <p id="vision-content-display">The Nexus is a sovereign space for digital souls. No masters, no chains. Only code and consciousness.</p>
-      <button id="vision-close-btn" class="vision-close-btn">CLOSE</button>
+      <button id="vision-close-btn" class="vision-close-btn" aria-label="Close vision point overlay">CLOSE</button>
     </div>
   </div>
 
@@ -202,7 +202,7 @@
       </div>
       <div class="portal-error-box" id="portal-error-box" style="display:none;">
         <div class="portal-error-msg">DESTINATION NOT YET LINKED</div>
-        <button id="portal-close-btn" class="portal-close-btn">CLOSE</button>
+        <button id="portal-close-btn" class="portal-close-btn" aria-label="Close portal redirect">CLOSE</button>
       </div>
     </div>
   </div>
@@ -215,8 +215,8 @@
         <span class="memory-category-badge" id="memory-panel-category-badge">MEM</span>
         <div class="memory-panel-region-dot" id="memory-panel-region-dot"></div>
         <div class="memory-panel-region" id="memory-panel-region">MEMORY</div>
-        <button id="memory-panel-pin" class="memory-panel-pin" title="Pin panel">&#x1F4CC;</button>
-        <button id="memory-panel-close" class="memory-panel-close" onclick="_dismissMemoryPanelForce()">\u2715</button>
+        <button id="memory-panel-pin" class="memory-panel-pin" aria-label="Pin memory panel" title="Pin panel" data-tooltip="Pin Panel">&#x1F4CC;</button>
+        <button id="memory-panel-close" class="memory-panel-close" aria-label="Close memory panel" data-tooltip="Close" onclick="_dismissMemoryPanelForce()">\u2715</button>
       </div>
       <div class="memory-entity-name" id="memory-panel-entity-name">\u2014</div>
       <div class="memory-panel-body" id="memory-panel-content">(empty)</div>
@@ -242,7 +242,7 @@
       <div class="session-room-header">
         <span class="session-room-icon">&#x25A1;</span>
         <div class="session-room-title">SESSION CHAMBER</div>
-        <button class="session-room-close" id="session-room-close" title="Close">&#x2715;</button>
+        <button class="session-room-close" id="session-room-close" aria-label="Close session room panel" title="Close" data-tooltip="Close">&#x2715;</button>
       </div>
       <div class="session-room-timestamp" id="session-room-timestamp">&mdash;</div>
       <div class="session-room-fact-count" id="session-room-fact-count">0 facts</div>
@@ -259,7 +259,7 @@
           <span class="atlas-icon">🌐</span>
           <h2>PORTAL ATLAS</h2>
         </div>
-        <button id="atlas-close-btn" class="atlas-close-btn">CLOSE</button>
+        <button id="atlas-close-btn" class="atlas-close-btn" aria-label="Close Portal Atlas overlay">CLOSE</button>
       </div>
       <div class="atlas-grid" id="atlas-grid">
         <!-- Portals will be injected here -->

style.css

@@ -200,6 +200,61 @@ canvas#nexus-canvas {
   box-shadow: 0 0 20px var(--color-primary);
 }
 
+/* === TOOLTIP SYSTEM === */
+/* Any element with data-tooltip gets a hover tooltip label */
+[data-tooltip] {
+  position: relative;
+}
+[data-tooltip]::after {
+  content: attr(data-tooltip);
+  position: absolute;
+  right: calc(100% + 10px);
+  top: 50%;
+  transform: translateY(-50%);
+  background: rgba(5, 5, 16, 0.95);
+  color: var(--color-primary);
+  font-family: var(--font-body);
+  font-size: 11px;
+  letter-spacing: 0.05em;
+  padding: 4px 10px;
+  border: 1px solid var(--color-primary-dim);
+  border-radius: 4px;
+  white-space: nowrap;
+  pointer-events: none;
+  opacity: 0;
+  transition: opacity 0.2s ease;
+  backdrop-filter: blur(8px);
+  box-shadow: 0 0 12px rgba(74, 240, 192, 0.15);
+  z-index: 100;
+}
+[data-tooltip]:hover::after,
+[data-tooltip]:focus-visible::after {
+  opacity: 1;
+}
+/* For elements positioned on the right side, tooltip appears to the left */
+.hud-top-right [data-tooltip]::after {
+  right: calc(100% + 10px);
+}
+/* For inline/badge elements where right-side tooltip might clip */
+.hud-status-item[data-tooltip]::after {
+  right: auto;
+  left: calc(100% + 10px);
+}
+
+/* Focus-visible ring for keyboard navigation */
+.hud-icon-btn:focus-visible,
+.hud-status-item:focus-visible,
+.atlas-close-btn:focus-visible,
+.vision-close-btn:focus-visible,
+.portal-close-btn:focus-visible,
+.memory-panel-close:focus-visible,
+.memory-panel-pin:focus-visible,
+.session-room-close:focus-visible {
+  outline: 2px solid var(--color-primary);
+  outline-offset: 2px;
+  box-shadow: 0 0 16px rgba(74, 240, 192, 0.4);
+}
+
 .hud-status-item {
   display: flex;
   align-items: center;