Bug: Table header status is not set correctly on table header columns

[zoltanhosszu]

When importing a table with column headers, the TableCellHeaderStatus is not set correctly.

Link to relevant code in Lexical codebase:
https://github.com/facebook/lexical/blob/30ada8475a779d3c7ded4323b8782f1d5483430c/packages/lexical-table/src/LexicalTableCellNode.ts#L341C1-L347C5

Steps To Reproduce

Set this as the editor value:

<table>
  <tr>
    <th><p>Name</p></th>
    <td><p>Email</p></td>
  </tr>
  <tr>
    <th><p>Alice</p></th>
    <td><p>alice@example.com</p></td>
  </tr>
</table>

Add a new row with $insertTableRowAtSelection(). The new row will be this:

...
  <tr>
    <td></td>
    <td></td>
  </tr>
</table>

Instead, it should be:

...
  <tr>
    <th></th>
    <td></td>
  </tr>
</table>

The current behavior

Table column headers can only get TableCellHeaderStates.ROW status.

The expected behavior

Table column headers should get TableCellHeaderStates.COLUMN or TableCellHeaderStates.BOTH if it's a header column.

Impact of fix

Editing existing tables with header column will be correct.

[etrepum]

For full fidelity imports generally JSON is used, there isn't generally enough information in HTML to determine if a header cell is intended to be a row or column so the simplest strategy is used in the default import code. Note that this import code is run for any imported HTML which includes content pasted from other applications with arbitrary structure. You can override it with the html config of your editor.