feat(angular): support Angular 21, drop Angular 16 and 17

[ShaneK]

Issue number: resolves #30907

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What is the current behavior?

Ionic Angular only currently supports Angular 16-20

What is the new behavior?

Ionic Angular now supports Angular 18 through 21 and drops 16 and 17. The ng16/ng17 test apps are removed, an ng21 app is added, and the tsconfigs are tightened for the 18+ minimum.

autocorrect on ion-input and ion-searchbar becomes a boolean (default false), mapped internally to the native 'on'/'off' attribute. This is required by TypeScript 5.9, which is required by Angular 21. It is the primary breaking change that forced this into a major version release of Ionic Framework.

Also bundles v9 housekeeping: @stencil/core bumped to 4.43.5 and TypeScript 5.9 in the React and Vue test apps.

Does this introduce a breaking change?

• Yes
• No

The following changes are required for migration:

• Apps on Angular 16 or 17 must upgrade to 18 or later.
• Existing NgModule projects upgrading to Angular 21 must add provideZoneChangeDetection() to bootstrapModule's applicationProviders in main.ts. ng-add only patches standalone app.config.ts, not main.ts, so the NgModule path is manual (documented in the schematic's JSDoc).
• autocorrect now takes true/false instead of 'on'/'off'. Replace autocorrect="on" with [autocorrect]="true" and autocorrect="off" (or the default) with false.

Other information

Preview:

• Autcorrect (no visual difference, just it's not broken despite the new type): input basic
• Angular 21

Current dev build (2025-06-02):

8.8.9-dev.11780414486.1df2bd72

Docs PR: ionic-team/ionic-docs#4529

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Project	Deployment	Actions	Updated (UTC)
ionic-framework	Ready	Preview, Comment	Jun 3, 2026 11:00pm

[thetaPC]

LGTM, with non-blocking requested change