parsing
Implement the foundational `mingling_picker` library along with its
companion
`mingling_picker_macros` crate. The picker provides:
- `Pickable` trait for parsing types from raw strings
- `PickerResult` enum modeling parse outcomes
- `Picker` struct for storing and indexing command-line arguments
- `PickerRequirement` struct for declarative parameter definitions
- `PickerPattern` family (1..32) of typed pattern structs via the
`internal_repeat` proc macro
- `req!` proc macro as a succinct builder for `PickerRequirement`
Re-export `mingling_picker::macros::*` from the `mingling` crate when
the
`picker` feature is enabled, replacing the previous wildcard re-export
of
`mingling_macros`.