feat(config): add validated profile core

libs/kaptan-config/src/storage.rs

@@ -0,0 +1,48 @@
+//! Persistence interface for complete validated candidate snapshots.
+
+use core::num::NonZeroU64;
+
+/// Storage-owned monotonically increasing committed snapshot generation.
+#[derive(Clone, Copy, Debug, Eq, Ord, PartialEq, PartialOrd)]
+pub struct Generation(NonZeroU64);
+
+impl Generation {
+    /// Creates a generation supplied only by a persistence backend.
+    pub const fn new(value: u64) -> Self {
+        match NonZeroU64::new(value) {
+            Some(value) => Self(value),
+            None => panic!("configuration generation must be nonzero"),
+        }
+    }
+
+    /// Parses an on-disk or wire generation, rejecting the factory sentinel.
+    pub const fn try_new(value: u64) -> Option<Self> {
+        match NonZeroU64::new(value) {
+            Some(value) => Some(Self(value)),
+            None => None,
+        }
+    }
+
+    /// Returns the committed generation value.
+    pub const fn get(self) -> u64 {
+        self.0.get()
+    }
+}
+
+/// Durable storage of complete configuration snapshots.
+///
+/// Flight implementations use a two-slot journal: a record contains a header,
+/// bounded CBOR payload, integrity check, and a commit marker written last.
+/// A backend must retain its previous valid record until the replacement is
+/// fully verified. Host file stores may implement the same interface without
+/// claiming flash power-loss semantics.
+pub trait ProfileStore<C> {
+    /// Backend-specific I/O or integrity failure.
+    type Error;
+
+    /// Loads the newest valid committed candidate, if one exists.
+    fn load(&mut self) -> Result<Option<(Generation, C)>, Self::Error>;
+
+    /// Persists one complete already-validated candidate atomically.
+    fn persist(&mut self, candidate: &C) -> Result<Generation, Self::Error>;
+}