jumoo-context: /full-test skill

Added /full-test to the jumoo-workflow plugin: an unattended test of a package on a fresh local Umbraco site, from a local build, a given version or the latest nightly
Checks cover what changed since the last release tag, regressions across existing features and previously fixed bugs, and a baseline of boot, migrations, restart persistence and the logs. Writes a test-report.md with the verdict, failures with repro steps, blocked checks and assumptions