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 `RenderResult` to support multiple user-defined print hooks
via a new `RenderResultPrint` struct containing content and output
mode. Add `bind_print_hook()` for custom sinks and reimplement
`immediate_output()` as a built-in hook. Update manual `Clone`,
`PartialEq`, `Eq`, and `Debug` implementations since hooks are opaque
closures.

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.

details