Add `mling update` to fetch the latest GitHub Actions artifact for the
current platform, stage it as a tarball in the data directory, and apply
it on the next wrapper invocation. The wrapper extracts the staged
package over the installation directory while skipping the running
executable, then removes the staged file.

Add the `class-add` command to create project classes from
templates registered in `.mling/classes.toml`. Supports name
derivation (snake_case, PascalCase, etc.), template expansion,
and shell completions.

Add `--pair` flag to output config values as `"key" = "value"` pairs,
and provide escaped formatting for display. Move config path resolution
to a helper function and expose the underlying hash map for rendering
and completion.

Add a new `cfg` command to view and edit configuration
items stored as key-value pairs in a JSON file.

Implement `mling proj-init` to generate projects from zip templates with
checklist-based configuration. Extracts template archive, moves
checklist for user editing, and expands `tmpl_`-prefixed files using
`just_template` with boolean rule evaluation from `rule.toml` for file
hides and display toggles.

Add `pkg-show` to display installed packages and their versions,
removing its NOT_IMPL marker from help. Include internal commands
to load enabled package paths and completion scripts.

Add package enable/disable functionality with version matching
for pkg-enable, and fix help text to reflect implemented commands.

Implement `mling uninstall` to remove installed packages by name or
name@version, with shell completion support. Rework install to build
release binaries, copy them plus completion scripts to a per-version
directory under the user data dir.