Previously, #[command] required at least one owned parameter for
args injection.  Now, if the first parameter is a reference or
there are no parameters, a synthetic entry parameter is inserted
so the function can still be used with #[chain].

Add a new `#[command]` attribute macro (feature-gated behind
`extra_macros`) that converts a plain function with a `Vec<String>`
parameter into a fully wired Mingling command. The macro generates a
`dispatcher!` call, a `#[chain]` wrapper, and a hidden module
re-exporting
all generated types.

Also add `CommandPattern` to the pathf pattern analyzer to recognize
`#[command]`-annotated functions and track their generated hidden
modules.