feat: add support for Angular 21

[AtofStryker]

• Closes N/A

Additional details

Adds support for Angular 21 within Cypress Component testing. Right now the Angular 21 projects needs zone.js as a devDependency as cypress/angular currently only supports zone.js. I have a follow up PR #33025 that adds a zoneless mount handler and defaults the scaffolding to cypress/angular-zoneless for Angular 21 applications

As Angular 21's change detection is a bit different from the legacy implementations, I refactored some of the angular fixtures to use signals instead of observables as signals are fully supported as of angular 18+

Steps to test

use the prepublished binaries to make sure scaffolding works on a new angular 21 project

How has the user experience changed?

Users will now be able to use Angular 21 without Cypress scaffolding warnings. NOTE: this currently still requires the zone.js devDependency until the zoneless mount handler is merged down. The intent is for both of these two be shipped at the same time but the work is considered separate.

PR Tasks

• Have tests been added/updated?
• Has a PR for user-facing changes been opened in cypress-documentation? chore: add angular 21 and zoneless documentation cypress-documentation#6326
• Have API changes been updated in the type definitions?

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Note

Adds full Angular 21 support (scaffolding, dev server, tests, fixtures) and updates docs/CI, with fixtures migrated to signals and async APIs.

• Angular 21 Support
  • Add new system-tests/projects/angular-21 (config, deps, tsconfig, yarn.lock) and include v21 in test matrices (component_testing_spec.ts, webpack-dev-server e2e).
  • Update @packages/scaffold-config to recognize/install Angular 21 (README.md, minVersion bumps for Angular packages, detection tests for CLI v20/21).
  • Adjust webpack-dev-server Angular handler tests for v20/21 configs and tsconfig generation behavior.
  • Update Cypress schematic tests to target angular-20 and angular-21.
• Fixtures/Specs Refactor
  • Migrate Angular example components from RxJS/HttpClient to signals (signal, model) and async fetch; remove obsolete service; update specs to use componentRef.setInput, drop HttpClientModule, and use async providers.
• Docs/Changelog
  • Add CLI changelog entry for 15.8.0 noting Angular 21 component testing support.
• CI
  • CircleCI workflow/variables branch filters updated to feat/support_angular_21.

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[cypress]

cypress    Run #67699

Run Properties:   Failed #67699  •  cc8305ae98: fix issue with incorrect placement of tsconfig in angular config

Project	cypress
Branch Review	feat/support_angular_21
Run status	Failed #67699
Run duration	23m 11s
Commit	cc8305ae98: fix issue with incorrect placement of tsconfig in angular config
Committer	Bill Glesias
View all properties for this run ↗︎

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Test results
Failures	7
Flaky	2
Pending	26
Skipped	0
Passing	765
View all changes introduced in this branch ↗︎

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Warning

Partial Report: The results for the Application Quality reports may be incomplete.

UI Coverage  63.16%
Untested elements	26
Tested elements	48

Accessibility  99.01%
Failed rules	0 critical   3 serious   1 moderate   0 minor
Failed elements	18

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Tests for review

  cypress\e2e\runner\retries.experimentalRetries.mochaEvents.cy.ts • 2 failed tests • app-e2e

View Output

Test		Artifacts
... > does not try to serialize error with err.actual as DOM node		Test Replay Screenshots
... > does not try to serialize error with err.actual as DOM node		Test Replay Screenshots

  cypress\e2e\runner\runner.ui.cy.ts • 3 failed tests • app-e2e

View Output

Test		Artifacts
src/cypress/runner > tests finish with correct state > no tests		Test Replay Screenshots
src/cypress/runner > other specs > file with empty suites only displays no tests found		Test Replay Screenshots
src/cypress/runner > reporter interaction > user can stop test execution		Test Replay Screenshots

  cypress\e2e\cypress-origin-communicator.cy.ts • 2 failed tests • app-e2e

View Output

Test		Artifacts
Cypress In Cypress Origin Communicator > primary origin memory leak prevention > cleans up the primaryOriginCommunicator events when navigating away from the /specs to /settings		Test Replay Screenshots
Cypress In Cypress Origin Communicator > primary origin memory leak prevention > cleans up the primaryOriginCommunicator events when navigating to run a different spec		Test Replay Screenshots

  cypress\e2e\specs_list_switcher.cy.ts • 0 failed tests • app-e2e

View Output

Test		Artifacts

  cypress\e2e\studio\studio-limitations.cy.ts • 0 failed tests • app-e2e

View Output

Test		Artifacts

The first 5 failed specs are shown, see all 17 specs in Cypress Cloud.

  cypress\e2e\create-from-component.cy.ts • 1 flaky test • app-e2e

View Output

Test		Artifacts
... > runs generated spec		Test Replay Screenshots

  cypress\e2e\cypress-origin-communicator.cy.ts • 1 flaky test • app-e2e

View Output

Test		Artifacts
Cypress In Cypress Origin Communicator > primary origin memory leak prevention > cleans up the primaryOriginCommunicator events when navigating away from the /specs to /runs		Test Replay Screenshots