fix(tools): update background-task and session-manager

Minor improvements to background task handling and session manager utilities.

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

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

src/tools/session-manager/utils.ts

@@ -75,7 +75,7 @@ export function formatSessionMessages(
   if (includeTodos && todos && todos.length > 0) {
     lines.push("\n\n=== Todos ===")
     for (const todo of todos) {
-      const status = todo.status === "completed" ? "✓" : todo.status === "in_progress" ? "→" : "○"
+      const status = todo.status === "completed" ? "[x]" : todo.status === "in_progress" ? "[-]" : "[ ]"
       lines.push(`${status} [${todo.status}] ${todo.content}`)
     }
   }