fix(session-manager): match todo filenames exactly

Stop sibling session IDs from colliding in stable JSON storage by requiring an exact todo filename match instead of a substring filter.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-opencode)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/tools/session-manager/storage.ts

@@ -277,7 +277,7 @@ export async function readSessionTodos(sessionID: string): Promise<TodoItem[]> {
 
   try {
     const allFiles = await readdir(TODO_DIR)
-    const todoFiles = allFiles.filter((f) => f.includes(sessionID) && f.endsWith(".json"))
+    const todoFiles = allFiles.filter((f) => f === `${sessionID}.json`)
 
     for (const file of todoFiles) {
       try {