refactor(workspace): enforce layered crate boundaries

crates/aether-provider/core/src/lib.rs

@@ -0,0 +1,11 @@
+//! Provider domain contracts independent from transport and persistence.
+
+mod capability;
+mod catalog;
+mod health;
+mod policy;
+
+pub use capability::ProviderCapability;
+pub use catalog::{ProviderConfigError, ProviderDescriptor};
+pub use health::ProviderHealth;
+pub use policy::ProviderEligibilityPolicy;