refactor(workspace): enforce layered crate boundaries

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

@@ -0,0 +1,9 @@
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+pub enum ProviderHealth {
+    Unknown,
+    Healthy,
+    Degraded,
+    Unavailable,
+}