fix: sanitize all invalid characters in transformTypeName schema names
The previous fix (PR #696) handled []T slice type parameters but left
*T (pointer), map[K]V, and nested generics producing invalid OpenAPI 3
schema identifiers. For example:
Response[*model.User] -> Response_*model.User (invalid)
Response[map[string]model.User] -> Response_map[string]model.User (invalid)
Outer[Inner[model.User]] -> Outer_Inner[model.User] (invalid)
Replace the single []->Array- substitution with a general sanitizer
that handles all Go type syntax characters: [] -> Array-, [ -> -, ] -> -,
* -> (removed). Also replace the manual package path stripping with a
regex that correctly handles import paths appearing after type modifiers.
Add petstore example endpoint with nested generics to exercise the
nested case in the golden spec CI check.
Fixes remaining cases from #560.