feat(core): add move_task and rename_list to onyx-core

Add TaskRepository::move_task() to move tasks between lists and
rename_list() to rename lists on the filesystem. Adds rename_list
to the Storage trait with FileSystemStorage implementation.
Includes tests for both operations plus duplicate-name error case.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/onyx-core/src/repository.rs

@@ -68,6 +68,17 @@ impl TaskRepository {
         self.storage.delete_list(list_id)
     }
 
+    pub fn rename_list(&mut self, list_id: Uuid, new_name: String) -> Result<()> {
+        self.storage.rename_list(list_id, new_name)
+    }
+
+    pub fn move_task(&mut self, from_list_id: Uuid, to_list_id: Uuid, task_id: Uuid) -> Result<()> {
+        let task = self.storage.read_task(from_list_id, task_id)?;
+        self.storage.write_task(to_list_id, &task)?;
+        self.storage.delete_task(from_list_id, task_id)?;
+        Ok(())
+    }
+
     // Task ordering
     pub fn reorder_task(&mut self, list_id: Uuid, task_id: Uuid, new_position: usize) -> Result<()> {
         let mut metadata = self.storage.read_list_metadata(list_id)?;
@@ -320,6 +331,54 @@ mod tests {
         assert!(lists.is_empty());
     }
 
+    #[test]
+    fn test_move_task_between_lists() {
+        let temp_dir = TempDir::new().unwrap();
+        let mut repo = TaskRepository::init(temp_dir.path().to_path_buf()).unwrap();
+
+        let list_a = repo.create_list("List A".to_string()).unwrap();
+        let list_b = repo.create_list("List B".to_string()).unwrap();
+        let task = repo.create_task(list_a.id, Task::new("Movable".to_string())).unwrap();
+
+        repo.move_task(list_a.id, list_b.id, task.id).unwrap();
+
+        let tasks_a = repo.list_tasks(list_a.id).unwrap();
+        assert_eq!(tasks_a.len(), 0);
+
+        let tasks_b = repo.list_tasks(list_b.id).unwrap();
+        assert_eq!(tasks_b.len(), 1);
+        assert_eq!(tasks_b[0].title, "Movable");
+    }
+
+    #[test]
+    fn test_rename_list() {
+        let temp_dir = TempDir::new().unwrap();
+        let mut repo = TaskRepository::init(temp_dir.path().to_path_buf()).unwrap();
+
+        let list = repo.create_list("Old Name".to_string()).unwrap();
+        repo.rename_list(list.id, "New Name".to_string()).unwrap();
+
+        let renamed = repo.get_list(list.id).unwrap();
+        assert_eq!(renamed.title, "New Name");
+
+        // Old directory should be gone
+        assert!(!temp_dir.path().join("Old Name").exists());
+        assert!(temp_dir.path().join("New Name").exists());
+    }
+
+    #[test]
+    fn test_rename_list_duplicate_name() {
+        let temp_dir = TempDir::new().unwrap();
+        let mut repo = TaskRepository::init(temp_dir.path().to_path_buf()).unwrap();
+
+        repo.create_list("A".to_string()).unwrap();
+        let list_b = repo.create_list("B".to_string()).unwrap();
+
+        let result = repo.rename_list(list_b.id, "A".to_string());
+        assert!(result.is_err());
+        assert!(matches!(result.unwrap_err(), Error::InvalidData(_)));
+    }
+
     #[test]
     fn test_delete_list_removes_from_root_metadata() {
         let temp_dir = TempDir::new().unwrap();

crates/onyx-core/src/storage.rs

@@ -88,6 +88,8 @@ pub trait Storage {
     fn read_root_metadata(&self) -> Result<RootMetadata>;
     fn write_root_metadata(&mut self, metadata: &RootMetadata) -> Result<()>;
 
+    fn rename_list(&mut self, list_id: Uuid, new_name: String) -> Result<()>;
+
     fn read_list_metadata(&self, list_id: Uuid) -> Result<ListMetadata>;
     fn write_list_metadata(&mut self, metadata: &ListMetadata) -> Result<()>;
 }
@@ -464,6 +466,27 @@ impl Storage for FileSystemStorage {
         Ok(())
     }
 
+    fn rename_list(&mut self, list_id: Uuid, new_name: String) -> Result<()> {
+        let old_dir = self.list_dir_path(list_id)?;
+        let new_dir = self.list_dir_path_by_name(&new_name);
+
+        if new_dir.exists() {
+            return Err(Error::InvalidData(format!("A list named '{}' already exists", new_name)));
+        }
+
+        fs::rename(&old_dir, &new_dir)?;
+
+        // Update metadata timestamp
+        let metadata_path = new_dir.join(".listdata.json");
+        let content = fs::read_to_string(&metadata_path)?;
+        let mut metadata: ListMetadata = serde_json::from_str(&content)?;
+        metadata.updated_at = Utc::now();
+        let json = serde_json::to_string_pretty(&metadata)?;
+        fs::write(&metadata_path, json)?;
+
+        Ok(())
+    }
+
     fn read_root_metadata(&self) -> Result<RootMetadata> {
         self.read_root_metadata_internal()
     }