docs: document when and how tests are run (OSPS-QA-06.02)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Signed-off-by: Paradoxbound <paradoxbound@users.noreply.github.com>

Author: paradoxbound

README.md

@@ -225,7 +225,9 @@ npm test
 
 ### Testing
 
-Functional tests run against a live BookStack instance. Set these environment variables:
+Tests run automatically on every pull request and every push to `main` via the [Functional Tests](https://github.com/paradoxbound/bookstack-mcp/actions/workflows/functional-tests.yml) GitHub Actions workflow. The workflow also runs `npm audit`, OSV dependency scanning, and a TypeScript type-check on every run.
+
+To run tests locally, provide credentials for a live BookStack instance:
 
 ```env
 TEST_BOOKSTACK_URL=https://your-test-bookstack.com