[kaiserls]

Summary

• Port Fix environment discovery failure on unsupported platforms (fixes #39) prefix-dev/pixi-code#52 so an unsupported target-platform environment no longer hides valid Python environments (Failure when manifest contains non-native architecture environment prefix-dev/pixi-code#39).
• Handle package refresh failures and use Pixi's environment name for package queries.
• Resolve configured Pixi executable paths relative to workspace folders, expand ${workspaceFolder}, and provide a workspace CWD fallback.
• Document the changes and bump the extension version to 0.2.1.

Validation

• Unit tests: 5 passed, including unsupported-environment discovery, package refresh, path resolution, CWD, and a real subprocess from a path containing spaces.
• VS Code extension tests: 2 passed.
• Type checking, linting, formatting, and webpack build passed.

Please use a merge commit when merging; this branch contains separately scoped commits.