Add `Pickable` implementation for `bool` and the supporting `Matcher`
trait
with utility functions for argument matching. Expose `pickable_needed`
and
`matcher_needed` modules for downstream trait implementors.
Introduce the core pathfinding infrastructure with `ModulePathMapping`,
`MappingItem`, and `MinglingPathfinderError` types. Support recursive
module traversal, `pub use` re-export hoisting, and standard Rust
module resolution rules.