Meta Package Manager Files

[!NOTE] 6.4.0 is available on 🐍 PyPI and 🐙 GitHub.

• [apk] Add Alpine Linux's apk package manager with installed, outdated, search, install, upgrade, remove, sync, and cleanup support.
• [guix] Add GNU Guix package manager with installed, outdated, search, install, upgrade, remove, sync, and cleanup support.
• [macports] Add MacPorts package manager with installed, outdated, search, install, upgrade, remove, sync, and cleanup support.
• [ports] Add FreeBSD ports tree manager with installed, outdated, install, upgrade, upgrade_all, remove, sync, and cleanup support. Drives make-based source builds out of /usr/ports, delegates registry queries to pkg, and uses git for tree updates.
• [sfsu] Add sfsu (Scoop alternative) package manager with installed, outdated, search, install, upgrade, remove, sync, and cleanup support. Mutating operations delegate to Scoop.
• [xbps] Add XBPS (Void Linux) package manager with installed, outdated, search, install, upgrade, remove, sync, and cleanup support.
• [apm,apt,choco,composer,emerge,flatpak,opkg,sdkman,snap,zypper] Add remove operation. Closes {issue}1775.
• [composer] Fix install operation: use composer global require instead of composer global install.
• [apm,npm,pip] Add cleanup operation.
• [gem,winget] Add sync operation.
• [mpm] Add Delegate descriptor to capabilities.py for declarative cross-manager method delegation.
• [mpm] Add Python version and platform to --version output.
• [mpm] Add typed config_schema to the CLI group for configuration file validation.
• [mpm] Document pyproject.toml auto-discovery for per-project [tool.mpm] configuration.
• [mpm] Extend --table-format structured output to TOML, YAML, XML, JSON5, JSONC, and HJSON for all subcommands that produce machine-readable data (managers, installed, outdated, search, locate).
• [mpm] Change JSON output indentation from 4 to 2 spaces and stop sorting keys, aligning with click-extra defaults.
• [mpm] Rename --output-format / -o back to --table-format, aligning with the upstream click-extra default.
• [mpm] Make Chocolatey release job idempotent: check if version already exists on Chocolatey before pushing, and open a PR to update the nuspec after a successful publish.
• [mpm] Add Guix and Nix package definitions with automated update jobs on release; reorganize packaging/ directory into packaging/choco/, packaging/guix/, and packaging/nix/ subdirectories.
• [pip] Filter mpm's own dependency tree from outdated results to fix false positives in Homebrew-installed environments. Closes {issue}1767.
• [scoop] Fix CLI invocation in outdated operation.
• [winget] Fix search crash when no results are returned.
• [zypper] Skip install and remove tests on Linux CI runners: the RPM database at /var/lib/rpm is inaccessible on Ubuntu-based runners.

Full changelog: v6.3.0...v6.4.0