Function config_defaults_probe 

pub fn config_defaults_probe(
    env_vars: &[String],
) -> BTreeMap<String, ProbedConfigEntry>

Observe this SDK’s real config defaults and applicability, variable by variable. Lives here rather than in a probe binary so the executable contract test and the cross-language parity gate measure the same thing. Report what this SDK actually does with each named environment variable.

Used by both rust/tests/config_applicability.rs and the config_probe example that spec/check_config_parity.py shells out to, so the in-repo gate and the cross-language gate cannot disagree about what was measured.