fix: restore parent ol numId after nested list closes

[arthrod]

Summary

• Fixes ordered list numbering that restarts at "1." after a nested list closes
• Uses a stack (_ol_id_stack) to preserve parent list context during nesting

Problem

When an ordered list contains a nested list, items after the nested list were restarting numbering at "1." instead of continuing.

Example:

<ol>
  <li>First</li>      <!-- Shows as 1. ✓ -->
  <li>Second          <!-- Shows as 2. ✓ -->
    <ol>
      <li>Second.A</li>
      <li>Second.B</li>
    </ol>
  </li>
  <li>Third</li>      <!-- Was showing 1. ✗ (should be 3.) -->
</ol>

Root Cause

The handle_li function correctly uses current_ol_num_id to track list continuity. However, when a nested <ol> opens, current_ol_num_id is updated to a new value. When the nested <ol> closes, the parent's current_ol_num_id was not being restored.

Solution

Track current_ol_num_id in a stack to preserve parent context:

• On <ol> open: push current ID to stack before creating new one
• On <ol> close: pop from stack to restore parent's ID

Test plan

• Verify nested ordered lists maintain correct numbering
• Verify deeply nested lists (3+ levels) work correctly
• Verify mixed nested lists (ol inside ul inside ol) work correctly

[dfop02]

hey @arthrod , Just a kindly reminder. Thanks!