fix(grid): Recalculate horizontal size cache when scrolling horizontally with autosized columns #

[mddragnev]

Closes #17392

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 targets a Grid horizontal virtualization issue where many width="auto" columns can leave a large blank gap at the end of horizontal scrolling, by ensuring the horizontal size caches are recalculated after auto-sizing columns that enter the viewport.

Changes:

• Trigger cache rebuilds for the header and horizontal IgxGridForOfDirective instances after auto-sizing columns in view.
• Add a unit test intended to validate that the horizontal size cache is rebuilt when navigating horizontally to columns that are auto-sized.

Reviewed changes

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

File	Description
projects/igniteui-angular/grids/grid/src/grid-base.directive.ts	Rebuilds horizontal virtualization size caches after auto-sizing columns in view to prevent stale cached widths during horizontal scroll.
projects/igniteui-angular/grids/grid/src/column.spec.ts	Adds a unit test for verifying horizontal size cache behavior when auto-sized columns are scrolled into view.