Your task is to debug and explain why the `@media` section in the following HTML/CSS code is not triggering when the screen size drops below the 724 pixels.

Code:
```
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Responsive Flexbox with Dropdown</title>
  <style>
    /* 1. Basic Setup (for presentation) */
    body {
      font-family: system-ui, sans-serif;
      margin: 0;
      padding: 1.5rem;
      background-color: #f0f2f5;
    }
    .main-content, .sidebar {
      padding: 1.5rem;
      border-radius: 8px;
    }
    .main-content { background-color: #0d6efd; color: white; }
    .sidebar { background-color: #e9ecef; }
    
    ul { list-style: none; padding: 0; margin: 0; }
    li { padding: 0.5rem 0; border-bottom: 1px solid #ccc; }
    li:last-child { border: none; }


    /* 2. The Core Flexbox Layout Pattern */
    .layout-container {
      display: flex;
      flex-wrap: wrap-reverse; /* Allows stacking when space is tight */
      gap: 1.5rem;
    }

    .main-content {
      /* This sets the ideal minimum width for the main content.
         If the container can't fit this + the sidebar, it wraps. */
      flex-basis: 450px;
      flex-grow: 1; /* Allows it to grow and fill empty space */
      
      /* THIS IS THE FIX FOR OVERFLOW:
         It allows a flex item to shrink below its content's natural size. */
      min-width: 0;
    }

    .sidebar {
      /* flex-grow is 0 by default, flex-shrink 1, flex-basis auto */
      flex-basis: 250px; /* The sidebar's "fixed" width */
      min-width: 0;      /* Also apply here for robustness */
    }


    /* 3. Responsive Dropdown Logic */
    .sidebar details {
      width: 100%;
    }

    /* ---- WIDE SCREEN (default sidebar panel) ---- */
    /* When the screen is wide, we treat the sidebar as a static panel. */
    .sidebar summary {
      cursor: default; /* Not a button on wide screens */
      font-weight: bold;
    }
    
    /* Hide the default dropdown arrow on wide screens */
    .sidebar summary::marker,
    .sidebar summary::-webkit-details-marker {
      display: none;
    }

    /* ---- NARROW SCREEN (sidebar becomes a dropdown) ---- */
    /* The layout wraps at roughly 450 + 250 + 24 = 724px. */
    @media (max-width: 724px) {

      .sidebar {
        /* On narrow screens, the sidebar becomes a simple box for the dropdown */
        padding: 0;
        background-color: transparent;
        flex-grow: 1;
      }

      .sidebar summary {
        /* Make the summary look like a clickable button */
        cursor: pointer;
        padding: 1rem 1.5rem;
        border-radius: 8px;
        background-color: #198754;
        color: white;
        font-weight: normal;
      }
      
      /* Restore the default dropdown arrow on narrow screens */
      .sidebar summary::marker,
      .sidebar summary::-webkit-details-marker {
        display: list-item;
      }

      .sidebar ul {
        /* Style the dropdown content area */
        margin-top: 0.5rem;
        padding: 1rem;
        background-color: #e9ecef;
        border-radius: 8px;
      }
    }
  </style>
</head>
<body>

  <h1>Responsive Layout</h1>
  <p>Resize your browser window. Below ~724px, the sidebar will transform into a clickable dropdown menu.</p>

  <div class="layout-container">
    <main class="main-content">
      <h2>Main Content</h2>
      <p>I am the main content. My <code>min-width</code> is now `0`, so I will never cause the page to overflow. The layout wrapping is handled by `flex-basis` instead.</p>
    </main>

    <aside class="sidebar">
      <!-- The 'open' attribute makes the sidebar visible by default on wide screens -->
      <details open>
        <summary>Sidebar Menu</summary>
        <ul>
          <li><a href="#">Home</a></li>
          <li><a href="#">Profile</a></li>
          <li><a href="#">Settings</a></li>
          <li><a href="#">Logout</a></li>
        </ul>
      </details>
    </aside>
  </div>

</body>
</html>
```