fix(todo): make Todo id field optional for OpenCode beta compatibility

- Make id field optional in all Todo interfaces (TodoInfo, Todo, TodoItem)
- Fix null-unsafe comparisons in todo-sync.ts to handle missing ids
- Add test case for todos without id field preservation
- All tests pass and typecheck clean

src/cli/run/types.ts

@@ -34,10 +34,10 @@ export interface RunContext {
 }
 
 export interface Todo {
-  id: string
-  content: string
-  status: string
-  priority: string
+  id?: string;
+  content: string;
+  status: string;
+  priority: string;
 }
 
 export interface SessionStatus {