Notification after a long running command finishes

Description of the new feature/enhancement

It would be awesome to add an option for a notification bubble or sound after a long running command. Long running command can be configurable but a sane default could be 10 seconds.

The scenario for this would to switch users from a pull to push model. Without notifications, a user would have to constantly "pull" their terminal to see if their command is done. Switching to push removes the cognitive overhead of having to constantly pull and instead be pushed only once the command is done running.

Current workarounds

• Run a script that creates a notification after the command is done: long_command; notification.py

Extra asks

Beyond allowing for notifications, it would also be helpful if users were provided a hook. Here are some scenarios the hook can cover:

• Hitting an API to report the run length of the command (Useful for engineering systems)
• Changing the color of your smart LEDs (Think of all the things Makers could do!)
• Context aware notifications (If the script name contains 'foo' then do then, otherwise do that

Other Terminal support

• iTerm has this as a feature: https://www.iterm2.com/documentation-shell-integration.html#:~:text=Alert%20on%20next%20mark,in%20another%20window%20or%20tab.

Proposed technical implementation details (optional)

The issue names no files, tests, or entry points. Start by reviewing the requested configurable threshold, notification behavior, and optional hook scenarios, then compare them with the linked iTerm shell-integration reference. Done should mean an agreed scope for completion notifications and hooks, including how the threshold is configured.