* feat: add Ubuntu support via provider-based architecture
Implement multi-system support using a provider pattern that enables
phpenv to work with both Homebrew (macOS/Linux) and APT (Ubuntu/Debian
with Ondřej Surý PPA).
- Add provider infrastructure with auto-detection and PHPENV_PROVIDER override
- Refactor existing Homebrew code into __phpenv_provider_homebrew_* functions
- Implement APT provider with PPA setup, shim-based version switching
- Update doctor, versions, and help commands to be provider-aware
- Use XDG-compliant shim directory (~/.local/share/phpenv/shims)
* fix: address PR #112 code review feedback
- Fix semver parsing for complex constraints like ">=8.1 <9.0"
- Add input validation for APT commands to prevent injection
- Use atomic symlink creation to prevent race conditions
- Fix extension uninstall to mirror install package mappings
- Replace unsafe glob with explicit binary list in cleanup
- Remove redundant PATH filtering logic
- Validate PHPENV_PROVIDER against supported providers
- Use exact matching for Homebrew tap names
- Use Fish's string escape for regex escaping
* fix: validate dpkg output before passing to sudo apt-get
Validates package names follow Debian naming rules before using them
in the sudo apt-get remove command. This prevents potential command
injection if dpkg output contains unexpected characters.
Addresses remaining Copilot feedback from PR #112.
