Remove outdated async documentation from GNMIClient module:
- Remove async context manager from feature list
- Remove async usage example from class docstring
The client now only documents synchronous usage patterns.
- Replace placeholder deps with click, pygnmi, and rich for CLI functionality
- Add fabric-orch CLI entry point via project.scripts
- Configure hatchling as build backend with wheel/sdist targets
- Add ruff linter configuration for code quality
- Add dev dependency group with ruff
- Alphabetize yang module imports