fix(mdxish): render and parse tables without <tr>

[maximilianfalco]

🎫 Resolve RM-15641

🎯 What does this PR do?

Fixes <Table> components where <thead> or <tbody> cells aren't wrapped in an explicit <tr>. This is valid HTML that browsers render fine, but MDXish was producing empty/broken tables because the conversion logic only looked for cells inside <tr> elements.

Two fixes in two files:

• mdxish-tables.ts — The phrasing-only renderer now checks whether a <thead>/<tbody> section has <tr> children. If not, it collects cells directly from the section and treats them as a single implicit row.
• mdxish-jsx-to-mdast.ts — The transformTable MDAST converter normalizes bare cells into an implicit <tr> wrapper before processing, so the existing row-based logic works unchanged.

🧪 QA tips

Paste this into a doc using the MDXish editor and verify it renders a table with headers "Hi" / "World" and body cells "Hello" / "Globe":

<Table>
  <thead>
    <td>Hi</td>
    <td>World</td>
  </thead>
  <tbody>
    <td>Hello</td>
    <td>Globe</td>
  </tbody>
</Table>

• Table renders with both header and body rows
• Switching to native <table> still works as before
• Tables with explicit <tr> wrappers are unaffected
• Tables with flow content (code blocks, lists) in bare cells still render

📸 Screenshot or Loom

Screen.Recording.2026-03-30.at.17.08.11.mov