add cached .env parsing and configurable root/file options to DotEnvLoader
extend Env::populate() with loader injection, scalar casting, attribute defaults, and EnvObj target overrides
introduce Env\Exception\MissingEnvironmentValue for clearer required-variable errors
update attributes (EnvName, EnvObj) to expose metadata for defaults and target classes
expand PHPUnit suite to cover defaults, type casting, custom nested hydration, and missing-variable failures
document advanced usage patterns in the README (defaults, typing, nested objects, custom .env location)