fix(mdxish): terminate html flow block when opener has trailing text

[maximilianfalco]

🎫 Resolve RM-16379

🎯 What does this PR do?

Magic blocks placed directly under an opening HTML tag with trailing text were rendering as literal text because CommonMark consumed them into the HTML flow block. The terminateHtmlFlowBlocks preprocessor only recognized lines that were purely tags or had a matched open+close pair, so <li> test slipped past isLineHtml and no blank-line terminator was inserted.

Adds a third regex (HTML_LINE_WITH_TRAILING_CONTENT_REGEX) for lines that start with a lowercase HTML tag followed by trailing text

🧪 QA tips

 <li> test
[block:parameters]
{
  "data": {
    "h-0": "Heading",
    "0-0": "Content"
  },
  "cols": 1,
  "rows": 1,
  "align": [
    "left",
    "left"
  ]
}
[/block]

verify that the table renders as expected

📸 Screenshot or Loom

Before	After

monorepo showcase