feat(ui): redesign with modern styling and resource display

UI Improvements:
- Add gradient backgrounds to all components
- Add smooth hover/active animations with transforms
- Add subtle shadows and glow effects
- Add animated progress bar shimmer effect
- Add gradient logo with text fill

Button Redesign:
- Add gradient backgrounds and hover effects
- Add shadow on hover with lift animation
- Add btn-xs size for compact buttons
- Improve Kill All button styling

Session Cards:
- Show resource usage (memory, messages)
- Color-coded usage indicators (green/yellow/red)
- Add kill button per session
- Click to switch active session and load terminal

Process Management:
- Add Kill All Sessions button in panel header
- Add killAllSessions() and deleteSession() methods
- Add formatBytes() helper for display
- Add selectSession() to switch between sessions

Performance:
- Add requestAnimationFrame batching for terminal writes
- Smooth 60fps rendering with write batching

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/web/public/index.html

@@ -242,9 +242,14 @@
 
     <!-- Sessions Panel (collapsible) -->
     <aside class="sessions-panel" id="sessionsPanel">
-      <div class="sessions-header" onclick="app.toggleSessions()">
-        <h3>Sessions <span class="session-count" id="sessionCount">0</span></h3>
-        <span class="toggle-icon" id="toggleIcon">▼</span>
+      <div class="sessions-header">
+        <div class="sessions-header-left" onclick="app.toggleSessions()">
+          <h3>Sessions <span class="session-count" id="sessionCount">0</span></h3>
+          <span class="toggle-icon" id="toggleIcon">▼</span>
+        </div>
+        <button class="btn btn-sm btn-danger kill-all-btn" onclick="event.stopPropagation(); app.killAllSessions()" title="Kill all sessions">
+          ✕ Kill All
+        </button>
       </div>
       <div class="sessions-list" id="sessionsList"></div>
     </aside>