Separate library from CLI concerns:
- Add Resolver callback type with Decision/Response structs for all
interactive decisions (map/struct, type name, tuple/list, shape
unification, shape naming, name collision)
- Move terminal I/O (Prompter) from library to cmd/jsonpaths
- Add public API: New(), ParseFormat(), Generate(), AutoGenerate()
- Add Format type with aliases (ts, py, json-paths, etc.)
- Fix godoc comments to match exported function names
- Update tests to use scriptedResolver instead of Prompter internals
- Update doc.go and README with current API
