fix(grid): preserve refs and return new array to reflect changes

[IvanKitanov17]

Closes #17317

Description

Motivation / Context

When using the addRow and deleteRow methods of the grid the data source is not being updated.

Type of Change (check all that apply):

• Bug fix
• New functionality
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Refactoring (no functional changes)
• Documentation
• Demos
• CI/CD
• Tests
• Changelog
• Skills/Agents

Component(s) / Area(s) Affected:

Grids

How Has This Been Tested?

• Unit tests
• Manual testing
• Automated e2e tests

Test Configuration:

• Angular version:
• Browser(s):
• OS:

Screenshots / Recordings

Checklist:

• All relevant tags have been applied to this PR
• This PR includes unit tests covering all the new code (test guidelines)
• This PR includes API docs for newly added methods/properties (api docs guidelines)
• This PR includes feature/README.MD updates for the feature docs
• This PR includes general feature table updates in the root README.MD
• This PR includes CHANGELOG.MD updates for newly added functionality
• This PR contains breaking changes
• This PR includes ng update migrations for the breaking changes (migrations guidelines)
• This PR includes behavioral changes and the feature specification has been updated with them
• Accessibility (ARIA, keyboard navigation, focus management) has been verified

[Copilot]

Pull request overview

This PR addresses #17317 by ensuring IgxGridComponent.addRow() / deleteRow() keep the originally bound data source in sync (instead of breaking the reference by reassigning grid.data) while still triggering the grid pipeline to reflect in-place mutations.

Changes:

• Updated the grid transaction pipe to always return a new array reference when transactions are disabled.
• Updated addRowToData / deleteRowFromData to mutate grid.data in place (preserving the original array reference) and clear summary caches instead of cloning/reassigning the data array.
• (Recommended) Add regression tests to assert the externally bound array is updated across repeated add/delete calls when transactions are disabled.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 4 comments.

File	Description
projects/igniteui-angular/grids/core/src/common/pipes.ts	Returns a shallow-copied array in IgxGridTransactionPipe when transactions are disabled so downstream pipeline/virtualization sees a new reference.
projects/igniteui-angular/grids/core/src/api.service.ts	Stops reassigning grid.data on add/delete (preserves bound array ref) and clears summary cache after in-place mutations.