Add a Gitea workflow that runs on pull requests and pushes to main. It defines two jobs:
- Python: sets up Python 3.12, installs pytest, and runs language-server tests under server/tests/python_tests with PYTHONPATH=libs.
- Node: sets up Node 20, installs npm deps (root and client), runs extension tests (node --test test/) and builds the extension (npm run package).
Workflow file added at .gitea/workflows/tests.yml.
