Remove `Title`, `Lower`, and `Upper` variants from
`ParserStyleNamingCase` as they are not valid naming conventions.

Replace boolean flags in `ProgramStdoutSetting` and `ProgramUserContext`
with semantic enum types, improving type safety and self-documentation.

BREAKING CHANGE: Boolean fields are replaced by enums, e.g.
`verbose`/`quiet`/`debug` become `verbosity`, `dry_run`/`force` become
`execution`.

Correct off-by-one word index computation and conditionally pass
option values only when non-empty to avoid spurious parsing.

Remove the BasicStructPattern from pathf's pattern analyzer to eliminate
noise from plain structs not associated with any Mingling macro.

Also clean up the now-unused `basic_struct` module and update the
integration test to assert plain structs are no longer collected.

Fix the method to use `eprintln!` instead of `println!` when
`immediate_output` is enabled, ensuring error output goes to stderr.

Update changelog and issue tracker notes for the enhanced
`default_completion` behavior.

When a concrete entry's custom completion handler produces a `Suggest`
value, combine it with the default subcommand suggestions instead of
replacing them entirely. `FileCompletion` still falls back to the
default completion since it cannot be meaningfully merged.

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.