Support `[[user.toggle-mutex]]` groups in rule.toml to enforce
mutually exclusive toggle options, and derive `program_crate_name`
from `program_name` using snake_case conversion.

Allow `proj-init` to accept a `<ref>@<variant>` template source
that resolves and caches templates from a git repository, falling
back to local directories for plain paths.

Replace the ZIP-based template archive workflow with direct
directory copying. Delete the `package-mling-tmpls` tool and
remove the `zip` dependency.

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 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.

Move the CLI binary from `src/main.rs` to `src/bin/cli.rs`
and move shared program generation into a new lib.rs module.

Add a new `explain <LINT>` command that queries the embedded lint
registry (generated by `build.rs`) and displays detailed information
about a specifoic lint, including its name, title, summary, active-on
target, default setting, and author.

Enable the `structural_renderer` feature and add `serde`/`serde_json`
dependencies to support JSON output rendering for command results.