fix(core): respect detach() on views attached to ApplicationRef - #71062

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines: https://github.com/angular/angular/blob/main/contributing-docs/commit-message-guidelines.md
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

• Bugfix
• Feature
• Code style update (formatting, local variables)
• Refactoring (no functional changes, no api changes)
• Build related changes
• CI related changes
• Documentation content changes
• angular.dev application / infrastructure changes
• Other... Please describe:

What is the current behavior?

Calling detach() on a view that is attached directly to ApplicationRef has no effect. detach() only clears the Attached flag, and that flag is only read when a view is reached through its parent. Root views are where the traversal starts, so they get checked anyway:

• Eager component or embedded view: checked on every tick()
• OnPush component: checked after markForCheck()
• zoneless: checked when a signal read in the template changes

The same component created through a ViewContainerRef respects detach(), and so does the ChangeDetectorRef injected inside the component (it points to the component view, not the root view).

The only way out today is appRef.detachView(), but the code calling detach() usually doesn't know the view is attached to ApplicationRef, and it also removes the view from the DOM.

Issue Number: #46690

What is the new behavior?

ApplicationRef skips detached views:

• when refreshing views
• in the dev mode checkNoChanges pass
• when deciding if another pass is needed, otherwise a dirty detached view would keep requesting passes until synchronize gives up with NG0103

detectChanges() on a detached view still checks it, and reattach() brings it back to regular change detection.

Does this PR introduce a breaking change?

• Yes
• No

Other information

This matches what detach() documents, but it is a behavior change for anyone calling detach() on a root view and relying on it still being checked. Happy to change the target or add a note if you think that's needed.