#7977 docs: add standalone routing guard example

[satanTime]

Closes #7977

Summary

• add a runnable standalone routing guard example using provideRouter
• link the routing guard guide to the standalone example and document the standalone test setup
• exclude the new example from pre-Angular-14 e2e targets where standalone APIs are unavailable

Validation

• COMPOSE_PROJECT_NAME=ngmocks_7977 sh test.sh root
• COMPOSE_PROJECT_NAME=ngmocks_7977 sh test.sh coverage
• COMPOSE_PROJECT_NAME=ngmocks_7977 sh test.sh a5es5
• COMPOSE_PROJECT_NAME=ngmocks_7977 sh test.sh a14
• COMPOSE_PROJECT_NAME=ngmocks_7977 sh test.sh a20
• COMPOSE_PROJECT_NAME=ngmocks_7977 docker compose run --rm ng-mocks npm run prettier:check

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (b51b56e) to head (55ab0ca).

Additional details and impacted files

@@            Coverage Diff            @@
##              main    #13311   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files          228       228           
  Lines         4168      4168           
  Branches      1187      1187           
=========================================
  Hits          4168      4168           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
• 📦 JS Bundle Analysis: Save yourself from yourself by tracking and limiting bundle sizes in JS merges.