fix: prevent duplicated cell content in TableData.grid when table_cel…

[vloum]

Title:
fix: prevent duplicated cell content in TableData.grid when table_cells is shorter than grid

Description:

Table

Problem

When the number of table_cells is less than the size of the grid in TableData.grid, the previous implementation would fill the remaining grid cells by repeatedly using the last cell's content. This resulted in duplicated content in the output tables, especially in the last row, which could be misleading and did not match the original document layout.

Solution

This PR introduces a counter to ensure that only the available table_cells are assigned to the grid. Any extra cells in the grid will remain empty, preserving the correct table structure and preventing unwanted duplication.

Example

Before (incorrect, duplicated content):

| 规格型号 | 名称/规格 | 原产地 | 数量 | 单价（元） | 总价（元） | 备注 |
|---|---|---|---|---|---|---|
| GH6785 | 颈椎理疗仪 | 广东佛山 | 10 | 4000 | 40000 |   |
| GH7698 | 腰椎理疗仪 | 广东佛山 | 22 | 8000 | 160000 |   |
|   |   |   |   |   |   |   |
|   |   |   |   |   |   |   |
| 合计：人民币（大写）贰拾万  元整（￥210000元） | 合计：人民币（大写）贰拾万  元整（￥210000元） | ...（repeated）|

After (correct, matches original layout):

| 规格型号 | 名称/规格 | 原产地 | 数量 | 单价（元） | 总价（元） | 备注 |
|---|---|---|---|---|---|---|
| GH6785 | 颈椎理疗仪 | 广东佛山 | 10 | 4000 | 40000 |   |
| GH7698 | 腰椎理疗仪 | 广东佛山 | 22 | 8000 | 160000 |   |
|   |   |   |   |   |   |   |
|   |   |   |   |   |   |   |
| 合计：人民币（大写）贰拾万  元整（￥210000元） |   |   |   |   |   |   |

Impact

• Only affects the behavior of TableData.grid.
• Output tables will now accurately reflect the original document, with no misleading repeated content.

Compatibility & Risk

• This is a bugfix and should not affect normal cases where the number of cells matches the grid size.
• No breaking changes are expected.

Reviewer Notes

• Please check if the new logic for breaking out of the assignment loop is robust for all edge cases.
• Consider if there is a more elegant way to handle this mapping, but the current fix addresses the immediate duplication issue.

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[dolfim-ibm]

@vloum what you observe is actually the expected behavior. The Docling markdown serializer is designed on-purpose to repeat the content of merged columns (and rows). This is because the markdown format doesn't have a syntax for it.

If you would like to get the proper merged columns, you could use the HTML serializer which will show your table correctly.
It is also valid to use HTML inside Markdown, this is now possible with the new serializer interface.

[vloum]

@dolfim-ibm get it! There is no problem with repeated merging, which can avoid missing information due to incorrect assignment of values ​​to some merged cells. However, I think it is unnecessary to repeat the assignment in the last row, and just keep the value empty. If there is a duplicate in the summary row like the last one, it will be considered abnormal data when it is sent to llm. The current code modification only limits the last value and does not affect the normal original logic of the information in the middle cells. Thank you~ I will close this PR depending on your thoughts.