Fix multiple critical bugs: continueSessionInChat, projects link, mode buttons

Bug fixes:
- Add missing showLoadingOverlay/hideLoadingOverlay functions to ide.js
  (previously only existed in sessions-landing.js, causing continueSessionInChat to fail)
- Add loading overlay CSS styles to main style.css
- Fix Projects button URL: /projects -> /claude/ide?view=projects
- Add ?view= URL parameter handling in ide.js initialization
- Add missing Native mode button to chat view (now has 3 modes: Chat, Native, Terminal)

These fixes resolve:
1. "Continue in Chat" button not working in sessions view
2. Projects button in landing page nav taking to wrong URL
3. Missing "Native" mode button (user referred to as "Full Stack mode")
4. Loading overlay not displaying in IDE

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

public/claude-ide/index.html

@@ -165,6 +165,22 @@
                             </div>
                         </div>
                     </div>
+                    <!-- Chat Mode Buttons -->
+                    <div class="chat-modes-bar" id="chat-modes-bar">
+                        <button class="mode-btn active" data-mode="auto" onclick="setChatMode('auto')" title="Chat Mode - AI assisted conversations">
+                            <span class="mode-icon">💬</span>
+                            <span class="mode-label">Chat</span>
+                        </button>
+                        <button class="mode-btn" data-mode="native" onclick="setChatMode('native')" title="Native Mode - Commands execute directly on your system">
+                            <span class="mode-icon">⚡</span>
+                            <span class="mode-label">Native</span>
+                        </button>
+                        <button class="mode-btn" data-mode="webcontainer" onclick="setChatMode('webcontainer')" title="Terminal Mode - Persistent terminal session">
+                            <span class="mode-icon">🖥️</span>
+                            <span class="mode-label">Terminal</span>
+                        </button>
+                    </div>
+
                     <div class="chat-input-container">
                         <div class="chat-input-wrapper">
                             <textarea id="chat-input"