fix: imports to use ES module syntax

[periakteon]

Description

The CLI error came from two things:

• the script was written like a Node CLI (require, process) but the repo TypeScript config didn’t expose Node globals/types for that file
• cmdComplete had a control-flow typing issue, so TypeScript still saw subtask as possibly undefined
  Why the fix was necessary:
• without it, the task-management tool itself couldn’t compile, so we couldn’t mark tasks complete or ask for the next ready tasks
• fixing the tool restored the workflow/tracking layer, which we’re actively using to execute the feature safely

Type of Change

• New feature (agent, command, tool)
• Bug fix
• Documentation
• Refactoring
• CI/CD

Checklist

• Tests pass locally
• Documentation updated (if needed)
• Follows CONTRIBUTING.md