Introduces .github/BRANCH_PROTECTION_GUIDE.md to document branch protection and CI requirements. Adds .github/workflows/pr-checks.yml for PR validation, including unit tests and code quality checks. Updates TESTING_QUICKSTART.md and tests/TEST_SUMMARY.md to use consistent status check notation and clarify test suite details.
Introduces a full test suite under the tests/ directory, including API, service, connector, and utility tests, along with fixtures and documentation. Expands Makefile with granular test commands for unit, integration, API, service, connector, coverage, and quick tests. Adds configuration files for pytest and coverage reporting, and provides a quickstart guide for testing workflow.
