refactor(shared): consolidate 13+ getMessageDir copies into single shared function

src/shared/opencode-message-dir.ts

@@ -1,8 +1,11 @@
 import { existsSync, readdirSync } from "node:fs"
 import { join } from "node:path"
-import { MESSAGE_STORAGE } from "../tools/session-manager/constants"
+import { getOpenCodeStorageDir } from "./data-path"
+
+const MESSAGE_STORAGE = join(getOpenCodeStorageDir(), "message")
 
 export function getMessageDir(sessionID: string): string | null {
+  if (!sessionID.startsWith("ses_")) return null
   if (!existsSync(MESSAGE_STORAGE)) return null
 
   const directPath = join(MESSAGE_STORAGE, sessionID)