Feature: Interactive task completion command (sugar complete)

[cdnsteve]

Problem

When Sugar is running and a task is already complete (e.g., migration already applied), the agent continues burning tokens verifying work that's done.

Current workaround:

1. sugar stop --force
2. sugar update <task-id> --status completed
3. sugar run

Proposed Solution

Add a sugar complete <task-id> command that:

1. Gracefully interrupts the running agent for that specific task
2. Marks the task as completed
3. Allows Sugar to continue with other tasks without full restart

Optional Enhancements

• sugar complete <task-id> --note "reason" - Add completion note
• sugar complete --current - Complete the currently running task
• Interactive prompt: "Task X is running. Mark as complete? [y/N]"

Use Case

User runs migration manually, sees it's done, wants to skip Sugar's verification and move to next task without wasting API credits.