chore: bootstrap nana-story M0

crates/nana-store/src/lib.rs

@@ -0,0 +1,20 @@
+use nana_domain::{RuntimeState, StoryNode};
+use thiserror::Error;
+
+#[derive(Debug, Error)]
+pub enum StoreError {
+    #[error("story not found: {0}")]
+    StoryNotFound(String),
+    #[error("storage backend is not initialized")]
+    NotInitialized,
+}
+
+pub trait StoryStore: Send + Sync {
+    fn append_node(&self, node: &StoryNode, state: &RuntimeState) -> Result<(), StoreError>;
+
+    fn load_state(
+        &self,
+        story_id: &str,
+        branch_id: &str,
+    ) -> Result<RuntimeState, StoreError>;
+}