…rove target selection and caching (#190)

feat: add strict input validation and robust plugin registration; improve target selection and caching

- Validate and normalize features input ('default' | 'full'); narrow type and throw on invalid values
- Throw on invalid version input (handled by top-level catch) for clearer failures
- Use GITHUB_WORKSPACE or fallback to current working directory to support local runs
- Ensure nu commands fail fast: add execOrThrow and apply to register and do-register steps
- Simplify getTargets by selecting platform map by feature and throw explicit unsupported target errors
- Cache fallback: when no nu_plugin_* binaries are found, cache extracted dir and emit a warning; keep permission fix
- Minor logging improvements (current directory, clearer messages)

* deps: Upgrade @biomejs/biome,lefthook & cspell

* ci skip

* feat: support proxies

* fix: remove redundant timeouts

* fix: make proxy agent singleton and specify types

…ion vulnerabilities (#195)