feat: add WORKON_HOME and XDG_DATA_HOME support for pipenv (Fixes #1185)

[karthiknadig]

Adds support for WORKON_HOME and XDG_DATA_HOME environment variables when discovering pipenv virtualenv directories.

Changes

• Added getPipenvVirtualenvDirs() function to pipenvUtils.ts that returns directories where pipenv virtualenvs may be stored
• Added comprehensive unit tests for the new function
• Added verbose tracing for debugging discovery issues

Discovery Priority

The function checks these locations in priority order:

1. WORKON_HOME (if set and exists) - commonly shared with virtualenvwrapper
2. XDG_DATA_HOME/virtualenvs (if XDG_DATA_HOME is set and path exists)
3. ~/.local/share/virtualenvs (Linux/macOS default)
4. ~/.virtualenvs (Windows default)

Testing

• 8 unit tests covering all env var scenarios, priority ordering, deduplication, and tilde expansion
• Tests use real temp directories for filesystem operations (since fs.existsSync cannot be stubbed)
• Cross-platform compatible (tested on Windows, patterns work for Linux/macOS)

Fixes #1185

[Copilot]

Pull request overview

This PR adds support for WORKON_HOME and XDG_DATA_HOME environment variables when discovering pipenv virtualenv directories. The implementation adds a new utility function that mirrors the logic from the PET (Python Environment Tools) server to ensure consistent environment discovery across platforms.

Changes:

• Added getPipenvVirtualenvDirs() function to centralize pipenv virtualenv directory discovery logic
• Added comprehensive unit tests covering all environment variable scenarios, priority ordering, and cross-platform behavior
• Added verbose logging for debugging pipenv discovery issues

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/managers/pipenv/pipenvUtils.ts	Adds getPipenvVirtualenvDirs() function that checks WORKON_HOME, XDG_DATA_HOME, and platform-specific default paths in priority order
src/test/managers/pipenv/pipenvUtils.getPipenvVirtualenvDirs.unit.test.ts	Comprehensive unit tests (8 test cases) covering environment variable scenarios, deduplication, tilde expansion, and cross-platform behavior