Fix clearCompletedExecutions for new pagination API format

Changes:
- Handle new pagination response format (data.executions vs data)
- Request up to 1000 executions to ensure all are checked
- Track successful deletions count
- Use terminal notification instead of alert
- Better error handling for individual delete failures

Fixes regression from Phase 5 pagination changes.

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

public/index.html

@@ -1094,8 +1094,9 @@
             if (!confirm('Delete all completed and failed executions?')) return;
 
             try {
-                const response = await fetch('/api/executions');
-                const executions = await response.json();
+                const response = await fetch('/api/executions?limit=1000'); // Get all executions
+                const data = await response.json();
+                const executions = data.executions || data; // Handle new pagination format
 
                 const toDelete = executions.filter(e => e.status === 'completed' || e.status === 'failed');
 
@@ -1104,15 +1105,17 @@
                     return;
                 }
 
+                let deleted = 0;
                 for (const execution of toDelete) {
-                    await fetch(`/api/executions/${execution.id}`, { method: 'DELETE' });
+                    const deleteResponse = await fetch(`/api/executions/${execution.id}`, { method: 'DELETE' });
+                    if (deleteResponse.ok) deleted++;
                 }
 
-                alert(`Deleted ${toDelete.length} execution(s)`);
+                showTerminalNotification(`Deleted ${deleted} execution(s)`, 'success');
                 refreshData();
             } catch (error) {
                 console.error('Error clearing executions:', error);
-                alert('Error clearing executions');
+                showTerminalNotification('Error clearing executions', 'error');
             }
         }