Refactor `build_dispatch_body` to take a caller-provided `no_match`
fallback token stream instead of hardcoding `build_entry_fallback`
calls. Thread the fallback through recursive calls so child paths are
preferred over exact endpoints at the same depth, matching the dynamic
dispatcher's longest-prefix-wins behavior.

Add `Metadata<B>` trait and `#[metadata(Entry)]` attribute macro
to attach arbitrary, compile-time-typed metadata to entries.
Implement `ProgramCollect::get_metadata<T>()` for runtime retrieval,
backed by a global registry populated by `register_metadata!`.

Extend `pathf` with `MetadataPattern` to resolve metadata types
across modules at build time. Add two examples demonstrating
metadata usage with and without pathf integration.

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.