refactor: Use real core types in graph_stub instead of simplified versions

Replace stub type definitions (Version, VersionDiff, IsolationLevel, etc.)
with imports from codegraph_core. This ensures the stub managers return
properly structured data that matches what the NAPI addon expects.

Changes:
- Import Version, VersionDiff, IsolationLevel, Snapshot, and ID types from codegraph_core
- Remove duplicate simplified type definitions
- Add comments explaining stub behavior
- Preserve stub implementation logic while using real types

This aligns the stub API with the real implementation and fixes compilation
issues in the NAPI addon where it expects Version objects with name,
description, and author fields.

Author: claude

crates/codegraph-api/src/graph_stub.rs

@@ -180,35 +180,10 @@ pub struct IntegrityReport {
     pub corrupted_data_count: usize,
 }
 
-// Stub manager types
-// Note: uuid and chrono are already imported at the top of this file
-
-// Define missing types that were incorrectly imported from codegraph_core
-pub type TransactionId = Uuid;
-pub type SnapshotId = Uuid;
-pub type VersionId = Uuid;
-
-#[derive(Debug, Clone)]
-pub struct IsolationLevel;
-
-#[derive(Debug, Clone)]
-pub struct Snapshot {
-    pub id: SnapshotId,
-    pub timestamp: DateTime<Utc>,
-}
-
-#[derive(Debug, Clone)]
-pub struct Version {
-    pub id: VersionId,
-    pub timestamp: DateTime<Utc>,
-}
-
-#[derive(Debug, Clone)]
-pub struct VersionDiff {
-    pub added_nodes: Vec<NodeId>,
-    pub modified_nodes: Vec<NodeId>,
-    pub deleted_nodes: Vec<NodeId>,
-}
+// Import the real types from codegraph_core instead of redefining them
+pub use codegraph_core::{
+    IsolationLevel, Snapshot, SnapshotId, TransactionId, Version, VersionDiff, VersionId,
+};
 
 #[derive(Clone)]
 pub struct ConcurrentTransactionManager;
@@ -218,7 +193,9 @@ impl ConcurrentTransactionManager {
         Self
     }
 
-    pub async fn begin_transaction(&self, _isolation_level: IsolationLevel) -> Result<TransactionId> {
+    pub async fn begin_transaction(&self, isolation_level: IsolationLevel) -> Result<TransactionId> {
+        // Stub implementation - just generate a new transaction ID
+        // In a real implementation, this would create a transaction with the specified isolation level
         Ok(Uuid::new_v4())
     }
 
@@ -248,15 +225,24 @@ impl GitLikeVersionManager {
         Self
     }
 
-    pub async fn create_version(&self, _name: String, _description: String, _author: String, _parent_versions: Vec<VersionId>) -> Result<VersionId> {
-        Ok(Uuid::new_v4())
+    pub async fn create_version(&self, name: String, description: String, author: String, parent_versions: Vec<VersionId>) -> Result<VersionId> {
+        let version_id = Uuid::new_v4();
+        let snapshot_id = Uuid::new_v4();
+
+        // In a real implementation, this would store the version
+        // For now, just return the ID
+        Ok(version_id)
     }
 
     pub async fn list_versions(&self) -> Result<Vec<Version>> {
+        // Stub implementation - return empty list
+        // In a real implementation, this would fetch from storage
         Ok(Vec::new())
     }
 
-    pub async fn get_version(&self, _id: VersionId) -> Result<Option<Version>> {
+    pub async fn get_version(&self, id: VersionId) -> Result<Option<Version>> {
+        // Stub implementation - return None
+        // In a real implementation, this would fetch from storage
         Ok(None)
     }