fix(igxGrid): In case zone is already stable emit detect and emit chu…

[MayaKirova]

…nkLoad.

Closes #17258

Description

Motivation / Context

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:

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 adjusts the grid’s vertical scroll handling to ensure chunkLoad and related post-scroll logic run even when NgZone is already stable (notably when the scroll listener is attached via runOutsideAngular), addressing the reported keyboard navigation regression after vertical scrolling (#17258).

Changes:

• Refactors the vertical scroll post-processing into a callback function.
• Adds a zone.isStable branch to trigger detectChanges() and invoke the callback immediately; otherwise waits for zone.onStable.

[mddragnev]

@MayaKirova The issue seems to be with a zoneless application. The provided sample in the issue does not have the provideZoneChangeDetection() provider which is currently needed for a lot of things in the grid. If we set that in the sample it works fine. However, you can easily reproduce this issue in the dev demos when you remove the provideZoneChangeDetection() from the main.ts file. Then, in each sample that has a vertical scroll the issue is reproducible. Since this is the second issue with zoneless apps in the past week we might need to prioritize the problem @dkamburov.