feat(cli): auto-resolve queueable step when --step omitted

[saraichinwag]

Summary

Fixes #82 - Simplify queue CLI for single-step flows

Before

wp datamachine flows queue add 29 --step=12_e5eda239-5bd7-4ae6-89f1-e21909115c98_29 "My prompt"

After

wp datamachine flows queue add 29 "My prompt"

How It Works

Added resolveQueueableStep() helper that:

1. Queries flow_config from database
2. Finds all steps with queue_enabled=true
3. If exactly 1 → returns that step_id
4. If 0 → returns error: "Flow X has no queueable steps"
5. If multiple → returns error listing step IDs

Methods Updated

• queueAdd
• queueList
• queueClear
• queueRemove
• queueUpdate
• queueMove

Testing

Tested locally on Flow 29 (single queueable AI step):

$ wp datamachine flows queue list 29
Total: 28 prompt(s) in queue. (queue_enabled: yes)

$ wp datamachine flows queue add 29 "Test prompt"
Success: Prompt added to queue. Queue now has 29 item(s).

Backward Compatibility

--step flag still works when provided, enabling explicit step selection for flows with multiple queueable steps.

[chubes4]

Main logic looks good and the auto-resolve behavior is sensible. One request: please update the CLI usage strings and examples in FlowsCommand so they no longer imply --step is required for queue add/list/clear/remove/update/move. Right now multiple error/usage messages still hard-require --step, which conflicts with the new auto-resolve path.

[saraichinwag]

Updated CLI usage strings (2758f2e3):

• Parameter description now mentions auto-resolution when flow has exactly one queueable step
• Examples simplified to show --step as optional
• Added explicit example showing when --step is required (multiple queueable steps)

Ready for re-review.

[chubes4]

Updates look good. Usage text now matches the auto-resolve behavior and includes an explicit --step example for multi-queue flows. Approving.