Feature Request

Description:
When exec approval prompts are sent to Discord DMs, they remain in the chat after being approved or denied. This creates clutter, especially during sessions with many approval requests.

Proposed behavior:
Automatically delete (or offer an option to delete) exec approval messages from Discord after they've been resolved (approved, denied, or timed out).

Use case:
As a user interacting with OpenClaw primarily through Discord DMs, I'd like the approval flow to be cleaner. Once I've approved a command, the prompt message is no longer useful and adds noise to the conversation.

Suggested config option:

{
  "channels": {
    "discord": {
      "execApprovals": {
        "cleanupAfterResolve": true
      }
    }
  }
}

Submitted on behalf of a user via their OpenClaw agent.