[Table Improvements] Fill table gaps

[juliaroldi]

When pasting a complex table, with different cell number in each row, fill the gaps with spanned cells, making the table model uniform.

[Copilot]

Pull request overview

This PR implements automatic gap-filling for tables with irregular row lengths, ensuring all rows have the same number of cells by adding spanned cells where needed. This is particularly useful when pasting complex tables from external sources that may have inconsistent cell counts per row.

Changes:

• Added logic to track the maximum column count across all table rows
• Implemented gap-filling that extends short rows with spanLeft cells matching the properties of the last cell in each row
• Added comprehensive test coverage for various gap-filling scenarios including simple short rows, header cells in short rows, and tables with colspan

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
packages/roosterjs-content-model-dom/lib/domToModel/processors/tableProcessor.ts	Implements the core gap-filling logic by tracking maxColumns and filling short rows with spanLeft cells that inherit properties from the last cell
packages/roosterjs-content-model-dom/test/domToModel/processors/tableProcessorTest.ts	Adds new test cases for gap-filling scenarios and updates existing tests to reflect the uniform table structure created by gap-filling

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