fix(compiler): report unclaimed property bindings on ng-template - #70345

PR Checklist

• 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) — N/A

PR Type

• Bugfix

What is the current behavior?

Property bindings on a literal <ng-template> element that are not claimed by any directive are never checked against the DOM schema during template type checking. Forgetting to import the directive in

@Directive({selector: 'ng-template[auiTypedOption]'})
export class TypedOptionDirective { auiTypedOption = input.required<any>(); }

@Component({imports: [], template: `<ng-template [auiTypedOption]="searchResult()"></ng-template>`})
export class TestComponent {}

compiles silently and only fails at runtime with NG0303, while the same binding on a <div> is reported as NG8002 at build time.

Issue Number: #69322

What is the new behavior?

A literal <ng-template> (tagName === 'ng-template') is treated like a regular element for the purpose of unclaimed inputs in the type-check block, so the missing import is reported as NG8002: Can't bind to 'auiTypedOption' since it isn't a known property of 'ng-template'. Bindings claimed by a matching directive (e.g. [ngTemplateOutlet], [ngIf]) are not reported. Synthetic Template nodes generated for structural directive shorthand are not affected, since their bindings are already checked on the wrapped element.

The shared fixture in template_mapping_spec.ts now also claims [ngIf]/[ngForOf] (and defines showMessage()), because the <ng-template [ngIf]> / <ng-template ngFor [ngForOf]> source-mapping scenarios relied on those bindings never being checked.

Does this PR introduce a breaking change?

• Yes
• No

Other information

Templates that previously compiled with an unclaimed binding on <ng-template> (and then failed at runtime) now get a build-time diagnostic, consistent with regular elements. Unclaimed output bindings on <ng-template> are intentionally left as-is since they are outside the scope of the issue.

Verified locally with //packages/compiler-cli/src/ngtsc/typecheck/test:test (the new test fails without the change), //packages/compiler-cli/test/ngtsc:ngtsc and //packages/language-service/test:test.

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