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/shared/session-utils.ts

@@ -3,20 +3,7 @@ import * as os from "node:os"
 import { existsSync, readdirSync } from "node:fs"
 import { join } from "node:path"
 import { findNearestMessageWithFields, MESSAGE_STORAGE } from "../features/hook-message-injector"
-
-export function getMessageDir(sessionID: string): string | null {
-  if (!existsSync(MESSAGE_STORAGE)) return null
-
-  const directPath = join(MESSAGE_STORAGE, sessionID)
-  if (existsSync(directPath)) return directPath
-
-  for (const dir of readdirSync(MESSAGE_STORAGE)) {
-    const sessionPath = join(MESSAGE_STORAGE, dir, sessionID)
-    if (existsSync(sessionPath)) return sessionPath
-  }
-
-  return null
-}
+import { getMessageDir } from "./opencode-message-dir"
 
 export function isCallerOrchestrator(sessionID?: string): boolean {
   if (!sessionID) return false