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/tools/session-manager/session-formatter.ts

@@ -44,7 +44,7 @@ export async function formatSessionList(sessionIDs: string[]): Promise<string> {
 export function formatSessionMessages(
   messages: SessionMessage[],
   includeTodos?: boolean,
-  todos?: Array<{ id: string; content: string; status: string }>
+  todos?: Array<{ id?: string; content: string; status: string }>
 ): string {
   if (messages.length === 0) {
     return "No messages found in this session."

src/tools/session-manager/storage.ts

@@ -73,8 +73,8 @@ export async function getAllSessions(): Promise<string[]> {
   return [...new Set(sessions)]
 }
 
-export function getMessageDir(sessionID: string): string {
-  if (!existsSync(MESSAGE_STORAGE)) return ""
+export function getMessageDir(sessionID: string): string | null {
+  if (!existsSync(MESSAGE_STORAGE)) return null
 
   const directPath = join(MESSAGE_STORAGE, sessionID)
   if (existsSync(directPath)) {
@@ -89,14 +89,14 @@ export function getMessageDir(sessionID: string): string {
       }
     }
   } catch {
-    return ""
+    return null
   }
 
-  return ""
+  return null
 }
 
 export function sessionExists(sessionID: string): boolean {
-  return getMessageDir(sessionID) !== ""
+  return getMessageDir(sessionID) !== null
 }
 
 export async function readSessionMessages(sessionID: string): Promise<SessionMessage[]> {

src/tools/session-manager/types.ts

@@ -34,10 +34,10 @@ export interface SessionInfo {
 }
 
 export interface TodoItem {
-  id: string
-  content: string
-  status: "pending" | "in_progress" | "completed" | "cancelled"
-  priority?: string
+  id?: string;
+  content: string;
+  status: "pending" | "in_progress" | "completed" | "cancelled";
+  priority?: string;
 }
 
 export interface SearchResult {