Empty separator convention for inputs/outputs is invalid table markdown syntax

This is a valid markdown table:

| input1 | input2 | | output |
| --- | --- | --- | --- |
| 1 | 2 | | 3 |

This isn't.

| input1 |input2|| output |
| --- | -------|| ------- |
| 1 | 2 || 3 |

It would be desirable to ensure all tables are rendered correctly, while preserving the same rules for input/output fields

Start by locating the table-rendering path responsible for converting the two example inputs into Markdown. Compare how empty separator cells are handled, then add coverage for both examples and verify that input/output field rules remain unchanged while the resulting tables render correctly.

Written by the indexing model from the issue text.