fix: auto-create session when attaching terminal

The attach button was failing with "Invalid session" error when:
- No active session exists (chatSessionId is null)
- The stored session ID no longer exists in Claude service

Changes:
- Auto-create new session when no active session exists
- Detect "Session not found" error and create new session
- Recursively retry attach after creating new session
- Update global session IDs and UI elements
- Better error messages and user feedback

The attach button now works seamlessly without requiring users to
manually create a session first.

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

public/claude-ide/terminal.js

@@ -1213,9 +1213,40 @@ class TerminalManager {
     const currentSessionId = window.chatSessionId;
 
     if (!currentSessionId) {
-      showToast('No active Claude Code session. Start a chat first!', 'warning');
+      showToast('No active session. Creating a new session...', 'warning');
+
+      // Create a new session automatically
+      try {
+        const res = await fetch('/claude/api/claude/sessions', {
+          method: 'POST',
+          headers: { 'Content-Type': 'application/json' },
+          body: JSON.stringify({ workingDir: process.env.HOME || '/home/uroma' })
+        });
+
+        const data = await res.json();
+
+        if (!data.success) {
+          throw new Error(data.error || 'Failed to create session');
+        }
+
+        const newSessionId = data.session.id;
+
+        // Update global session ID
+        window.chatSessionId = newSessionId;
+        window.attachedSessionId = newSessionId;
+
+        // Update UI
+        const sessionIdEl = document.getElementById('current-session-id');
+        if (sessionIdEl) sessionIdEl.textContent = newSessionId;
+
+        // Now attach to the new session
+        return await this.attachToSession(terminalId);
+      } catch (error) {
+        console.error('[TerminalManager] Error creating session:', error);
+        showToast('Failed to create session. Please try creating one from the chat panel.', 'error');
         return;
       }
+    }
 
     try {
       const res = await fetch(`/claude/api/terminals/${terminalId}/attach`, {
@@ -1226,7 +1257,19 @@ class TerminalManager {
 
       const data = await res.json();
 
-      if (!data.success) {
+      if (!res.ok || !data.success) {
+        // Handle "Session not found" error specifically
+        if (data.error && data.error.includes('not found')) {
+          showToast(`Session "${currentSessionId.substring(0, 12)}..." no longer exists. Creating a new one...`, 'warning');
+
+          // Clear the invalid session ID
+          window.chatSessionId = null;
+          window.attachedSessionId = null;
+
+          // Recursively call to create a new session
+          return await this.attachToSession(terminalId);
+        }
+
         throw new Error(data.error || 'Failed to attach');
       }