Add ProcessedItems CLI commands for dedup management

[saraichinwag]

Summary

Add WP-CLI commands for processed items (deduplication tracking). ProcessedItemsAbilities exist but have no CLI wrapper.

Running Version

v0.39.0

Abilities to Wrap

• datamachine/clear-processed-items - Clear by pipeline or flow scope
• datamachine/check-processed-item - Check if item was processed
• datamachine/has-processed-history - Check if flow step has any history

Proposed Commands

wp datamachine processed-items clear --pipeline=12
wp datamachine processed-items clear --flow=42
wp datamachine processed-items check --flow-step=<id> --source=rss --item=<guid>
wp datamachine processed-items history --flow-step=<id>

Priority

🟢 Low - Mostly useful for debugging dedup issues