Injection token for the application environment configuration.
A consumer-app utility: it gives application code (and app-level cngx
wiring such as feature flags in providers) a typed DI handle on the
environment.ts object instead of a direct module import, so the value
can be swapped per bootstrap and stubbed in tests. No cngx library code
reads it.
The token has no default factory. inject(ENVIRONMENT) without a
provideEnvironment() in the bootstrap providers throws a
NullInjectorError - deliberately, because a silently-empty environment
would turn missing wiring into wrong runtime behavior. Code that must
work without one reads it as inject(ENVIRONMENT, { optional: true })
and handles the null.