[Table Improvements] Add Shift Cells Table Operation

[juliaroldi]

Add new shift cells up and shift cells left table operations. These operations move the table cell content to the cells at left or above.

[Copilot]

Pull request overview

This PR adds new table-editing operations to shift selected table cell contents left or up, wires them through the public editTable API, and exposes them in the demo ribbon UI, with accompanying unit tests.

Changes:

• Extend table operation types with TableCellShiftOperation (shiftCellsLeft and shiftCellsUp) and export them from the types package.
• Implement shiftCells model API to move cell contents left or up based on rectangular cell selections, and integrate it into the editTable public API.
• Add comprehensive unit tests for shiftCells behavior and route the new operations through existing public API tests and demo ribbon menu entries.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
packages/roosterjs-content-model-types/lib/index.ts	Re-exports TableCellShiftOperation so it can be used by API and consumers.
packages/roosterjs-content-model-types/lib/enum/TableOperation.ts	Introduces TableCellShiftOperation union and includes it in TableOperation; JSDoc updated to describe new shift operations.
packages/roosterjs-content-model-api/test/publicApi/table/editTableTest.ts	Extends editTable routing tests to assert that shiftCellsLeft/shiftCellsUp call the shiftCells model API.
packages/roosterjs-content-model-api/test/modelApi/table/shiftCellsTest.ts	Adds detailed unit tests for shiftCells covering single/multiple cells, multi-row/column selections, edge positions, and 3×3 scenarios.
packages/roosterjs-content-model-api/lib/publicApi/table/editTable.ts	Wires new operations shiftCellsUp and shiftCellsLeft into the editTable switch to call shiftCells.
packages/roosterjs-content-model-api/lib/modelApi/table/shiftCells.ts	Implements shiftCells logic using getSelectedCells and mutateBlock to shift cell contents left or up by the selection width/height, clearing vacated cells.
demo/scripts/controlsV2/demoButtons/tableEditButtons.ts	Extends the demo ribbon “Delete” table menu with “Shift cells up/left” items and maps them to the new table operations for interactive testing.

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[Copilot]

The phrase "Move the table cell content to the cell at above" is grammatically incorrect; please change it to "Move the table cell content to the cell above" to match standard English and the style used elsewhere in this file.

Suggested change

	* Move the table cell content to the cell at above
	* Move the table cell content to the cell above