feat: add cypress/angular-zoneless testing harness for Angular 21 (also supports Angular 20)

[AtofStryker]

• Closes feat(angular): Add support for zoneless change detection in Angular 20 #31504
• Closes Cypress component tests not working without zone.js #30070

Additional details

Adds a zoneless component testing harness for Angular 20 (experimental) and Angular 21. Angular 21 ships with zoneless and Cypress will scaffold cypress/angular-zoneless for Angular 21+ projects.

Because this is likely going to be the next target for cypress/angular and the recommended pattern for data-binding is now signals, this testing harness will be remove autoDetectChanges as this happens naturally and autoSpyOutputs as @Output decorators are legacy and can be created manually via createSpyOutputs.

NOTE: when we merge the changes upstream in #33007 we need to call this out as BREAKING CHANGES

Additionally, with the addition of the zoneless mount handler, the angular-21 system test project needs it's own set of fixtures, which will eventually be moved into the main fixture directory (as a replacement) once Angular 18 and 19 support are officially dropped from Cypress.

After this releases, we need to update @cypress/schematic to support Angular 21 as the scaffolded files via the schematic CLI are not correct. I have a WIP of this on #33027 and it must be done AFTER this feature is released

Steps to test

How has the user experience changed?

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 cypress/angular-zoneless for Angular 20/21 and integrates it across CLI, scaffolding, CI, and system tests (including new Angular 21 project).

• Packages:
  • New: @cypress/angular-zoneless package providing zone.js-free Angular component mounting (mount, createOutputSpy, zoneless TestBed setup).
  • Angular (zoned): ensure signal output spy subscriptions are cleaned up by tracking subscriptions.
• CLI/Exports:
  • Include angular-zoneless in CLI build, exports, files, post-build copy, eslint ignores, and devDependencies.
• Scaffolding:
  • Auto-select cypress/angular-zoneless for projects with Angular >=21 (fallback to cypress/angular otherwise).
  • Support file generation tests accept both cypress/angular and cypress/angular-zoneless.
• CI:
  • Add npm-angular-zoneless build job; include in PR and main workflows and ready-to-release deps.
  • Update workflow branch filters and artifact persistence branch name.
• System Tests:
  • Add full Angular 21 project using cypress/angular-zoneless (configs, support, components, specs, assets).
  • Execute Angular 21 CT separately; adjust existing Angular tests/configs (e.g., styles file, rxjs-interop alias, provider key fix).
  • Update schematic tests matrix (Angular 19/20).
• Docs/Meta:
  • Link new changelog; list package in CONTRIBUTING; CLI changelog notes zoneless support.

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[cypress]

cypress    Run #67744

Run Properties:   Failed #67744  •  2d84ab60c6: make active fixture sync and update angular-21 examples to signals where applica...

Project	cypress
Branch Review	feat/add_zoneless_angular_harness
Run status	Failed #67744
Run duration	20m 38s
Commit	2d84ab60c6: make active fixture sync and update angular-21 examples to signals where applica...
Committer	Bill Glesias
View all properties for this run ↗︎

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Test results
Failures	1
Flaky	2
Pending	27
Skipped	0
Passing	797
View all changes introduced in this branch ↗︎

UI Coverage  62.34%
Untested elements	27
Tested elements	48

Accessibility  98.98%
Failed rules	0 critical   3 serious   1 moderate   0 minor
Failed elements	19

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Tests for review

  cypress\e2e\runner\retries.experimentalRetries.mochaEvents.cy.ts • 1 failed test • app-e2e

View Output

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

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

View Output

Test		Artifacts
... > displays each run with correct information		Test Replay Screenshots

[AtofStryker]

we have to downgrade the test because the zoneless handler isn't supported within the binary yet (see the PR description)