Dispatchers are now always registered at compile time, removing the
`with_dispatcher` / `with_dispatchers` methods and the
`PathfinderConfig` API. The `dispatch_tree` feature now only controls
the matching strategy (trie vs linear list).

Move the REPL's argument splitting logic into a new public `utils`
module exposing the `ArgumentSplitter` trait for reuse by downstream
code.

Change `HookPreDispatchInfo.arguments` from `&[String]` to `&mut
Vec<String>`
so hooks can rewrite command-line arguments before dispatch.

Refactor program configuration types into a dedicated public `config`
module under `mingling_core`, making `StructuralRendererSetting`
accessible via `mingling_core::config` instead of the crate root.

Update all internal references and setup modules to use the new
`config::` path convention.