Improve docs coverage and accuracy

[dereuromark]

Summary

• add dedicated runtime API, circular dependency, and JSON Schema docs
• fix stale validation, CLI, XML namespace, and importer output documentation
• expand TypeScript and README docs so documented behavior matches current implementation

Verification

• composer cs-fix
• vendor/bin/phpunit

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.70%. Comparing base (5b32a8b) to head (81547b7).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##             master     #104   +/-   ##
=========================================
  Coverage     82.70%   82.70%           
  Complexity     1486     1486           
=========================================
  Files            42       42           
  Lines          3660     3660           
=========================================
  Hits           3027     3027           
  Misses          633      633           

☔ 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.