/clean

Remove old sprint directories with safety checks and archiving options

# Clean Sprints Command

You are cleaning up old sprint directories.

## IMPORTANT WARNING

**Sprint directories contain valuable artifacts:**
- Specification files (api-contract.md, backend-specs.md, etc.)
- Implementation reports from agents
- Status summaries
- Test reports

**The user is responsible for:**
- Creating checkpoints (git commits) before cleanup
- Backing up important sprint data
- Deciding which sprints to keep

## Workflow

### Step 1: List Existing Sprints



Show the user:
- Sprint directories found
- Last modified dates
- Size of each directory

### Step 2: Confirm Acti...