## Milestone 3: Workstreams

### Workstream Data Model

28. **Implement workstream storage** (`internal/storage/workstreams.go`)
    ```go
    type WorkstreamsFile struct {
        CurrentWorkstream string
        Workstreams      map[string]*Workstream
    }
    
    func LoadWorkstreams(path string) (*WorkstreamsFile, error)
    func (w *WorkstreamsFile) Save(path string) error
    ```

29. **Create workstream manager** (`internal/core/workstream_manager.go`)
    - `CreateWorkstream(name string, base string) error`
    - `GetCurrentWorkstream() (*Workstream, error)`
    - `SwitchWorkstream(name string) error`
    - `ListWorkstreams() ([]*Workstream, error)`
    - `AddCommitToWorkstream(sha, message string) error`

### Workstream Commands

30. **Implement onx new** (`internal/commands/new.go`)
    ```go
    func New(repo *Repository, name string) error {
        // 1. Fetch latest from origin/main
        // 2. Create workstream entry
        // 3. Set as current workstream
        // 4. Update workspace to base commit
        // 5. Log to oplog
    }
    ```

31. **Implement onx list** (`internal/commands/list.go`)
    - Read workstreams.json
    - Format output with current indicator (*)
    - Show commit count per workstream
    - Color code output for better readability

32. **Implement onx switch** (`internal/commands/switch.go`)
    ```go
    func Switch(repo *Repository, name string) error {
        // 1. Save current ephemeral state
        // 2. Load target workstream
        // 3. Checkout latest commit in workstream
        // 4. Update current_workstream
        // 5. Restore workspace state
        // 6. Log to oplog
    }
    ```

33. **Add workstream validation**
    - Validate workstream names (no special chars)
    - Check for uncommitted changes before switch
    - Prevent duplicate workstream names