refactor: update frontend and testing guidelines

[nicobytes]

This pull request updates the frontend documentation and meta-rules to standardize and enforce the use of @dotcms/utils-testing createFake functions for domain object mocks in tests, and to clarify styling best practices. The changes emphasize avoiding manual mocks for domain objects and prioritizing PrimeFlex/PrimeNG for styling, with BEM/custom SCSS as a fallback.

Testing Standards and Mock Data:

• Updated all relevant documentation to require using @dotcms/utils-testing createFake functions (e.g., createFakeContentlet, createFakeLanguage) for domain object mocks in tests, and to explicitly prohibit manual mocks for these objects. Provided a comprehensive reference table of available createFake functions and example usage. [1] [2] [3] [4] [5] [6] [7]
• Updated context and rule files to reflect the new mocking standard and reinforce using createFake functions in all test-related guidance.

Styling Standards:

• Updated styling guidelines to prioritize PrimeFlex utility classes and PrimeNG components for layout and UI, with BEM and custom SCSS reserved only for cases where utilities/components do not suffice. Clarified avoidance of hardcoded colors/spacing and use of design tokens or theme variables. [1] [2]

Documentation Cleanup:

• Removed a redundant frontend documentation index entry.

#32713

This PR fixes: #32713

[Copilot]

Pull request overview

This PR updates frontend testing and styling documentation, along with AI/context rules, to standardize how mocks and styles are used in the Angular monorepo. It deprecates an older, redundant frontend unit testing doc in favor of a single, richer testing guide and aligns Cursor/CI instructions with that guide.

Changes:

• Removed the legacy docs/testing/FRONTEND_UNIT_TESTS.md in favor of docs/frontend/TESTING_FRONTEND.md as the canonical frontend testing guide.
• Updated docs/frontend/TESTING_FRONTEND.md, .github/instructions/frontend.instructions.md, and Cursor rule files to require @dotcms/utils-testing createFake* functions for domain object mocks and to clarify mocking patterns.
• Tightened styling guidance in frontend instructions and context rules to prioritize PrimeFlex/PrimeNG and treat custom SCSS/BEM as an exception, plus minor cleanup to the Angular docs index.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
docs/testing/FRONTEND_UNIT_TESTS.md	Fully removed now-redundant frontend unit testing guide in favor of the centralized TESTING_FRONTEND.md documentation.
docs/frontend/TESTING_FRONTEND.md	Expanded with a required createFake* usage section, a reference table of fake creators, explicit “no manual domain mocks” rules, and updated best-practices/location info (with one outdated path noted below).
docs/frontend/ANGULAR_STANDARDS.md	Cleaned up the “See also” index by removing a redundant README entry, keeping the Angular standards index lean.
.github/instructions/frontend.instructions.md	Updated the high-level frontend instructions to strongly prefer PrimeFlex/PrimeNG for styling and to mandate @dotcms/utils-testing createFake* functions for domain mocks in tests.
.cursor/rules/test-context.mdc	Adjusted test context rules so Cursor explicitly nudges towards createFake* mocks over manual domain object construction.
.cursor/rules/frontend-context.mdc	Synced frontend context rules with the new styling and mocking standards, ensuring agents prefer PrimeFlex/PrimeNG and @dotcms/utils-testing in generated code/tests.