Feature request: option to suppress async hook completion messages

Problem

When using async: true hooks, Claude Code displays completion messages like:

⎿  Async hook UserPromptSubmit completed
⎿  Async hook Stop completed

These messages appear after every prompt/response cycle and can be noisy, especially when multiple hooks are registered. There is currently no way to suppress them.

Proposed Solution

Add a configuration option to suppress these completion messages, for example:

{
  "hooks": {
    "UserPromptSubmit": [{
      "hooks": [{
        "type": "command",
        "command": "python3 /path/to/hook.py",
        "async": true,
        "silent": true
      }]
    }]
  }
}

Or a global setting:

{
  "suppressAsyncHookMessages": true
}

Use Case

Users who use async hooks for background tasks (logging, session tracking, analytics, etc.) don't need to see these completion messages — they're purely informational and add visual noise to every interaction.

Current Workaround

There is none. Removing async: true suppresses the messages, but causes hooks to block the UI.