Fix cursor position for arrow up

[juliaroldi]

When pressing arrow up, move the cursor to the top of the cell, so the cursor can be placed at the cell above.
Before:

After:

[Copilot]

Pull request overview

Adjusts table keyboard navigation so pressing ArrowUp preserves horizontal caret placement by computing the insertion point at the top edge of the target cell, preventing the cursor from getting “stuck” and enabling movement into the cell above.

Changes:

• Update ArrowUp caret hit-testing to use the target cell’s rect.top instead of rect.top - 1.
• Expand/add a unit test scenario for ArrowUp to validate horizontal-position preservation when the browser initially lands in the wrong column.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
packages/roosterjs-content-model-core/lib/corePlugin/selection/SelectionPlugin.ts	Tweaks the Y coordinate passed to getNodePositionFromEvent for ArrowUp within table navigation.
packages/roosterjs-content-model-core/test/corePlugin/selection/SelectionPluginTest.ts	Updates/expands ArrowUp test coverage around preserving horizontal caret placement in tables.

Comments suppressed due to low confidence (1)

packages/roosterjs-content-model-core/test/corePlugin/selection/SelectionPluginTest.ts:2216

• This new test mocks getNodePositionFromEvent but never asserts the coordinates it is called with. Since the production change is specifically about the Y coordinate used for ArrowUp (rect.top vs rect.top - 1), the test should include an expectation that getNodePositionFromEvent is invoked with the target cell's top Y value (and the original cursorRect.left) so the fix is actually covered and protected from regression.

            // Mock getNodePositionFromEvent to return a specific position in td6 (middle row, third column)
            const targetNode = testTd6_text;
            const targetOffset = 1;
            spyOn(getNodePositionFromEventFile, 'getNodePositionFromEvent').and.returnValue({
                node: targetNode,
                offset: targetOffset,
            });

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