Rename the internal fallback type and its associated `ProgramCollect`
plumbing from `ErrorDispatcherNotFound`/`build_dispatcher_not_found` to
`EntryFallback`/`build_entry_fallback`, along with the generated enum
variant and pack type. Update all documentation, examples, and tests
accordingly.

Add `add_suggest()` and `add_suggest_with_description()` methods to
`Suggest` for ergonomic batch population of suggestion sets from
collections of strings.

Update the `suggest!` macro to use these new methods and accept
expressions beyond string literals for suggestion items.

Update all references across docs, examples, and configuration files to
use the shorter `extras` feature name.

Add a `From<pack_Type> for crate::Entry` implementation in
`dispatcher!()` macro and a default `Entry` pack type in
`gen_program!()` for ergonomic program entry handling

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].

Move pathf type resolution from `program_final_gen` to `gen_program` and
isolate generated code inside `__this_program_impl` to prevent namespace
pollution

program_final_gen