Add generic run control for workflows

[chubes4]

Summary

• Add WP_Agent_Run_Control as a shared addressable run-control primitive for run IDs, statuses, persistence, and cancellation requests.
• Keep chat run-control behavior intact by delegating chat lifecycle methods to the shared primitive while preserving chat-specific queue helpers.
• Wire workflow runs into shared run-control and stop on cancel_requested before the next step, including checks inside foreach iteration/nested-step boundaries.
• Add workflow smoke coverage proving cancellation stops before the next step.

Testing

• composer test
• php tests/workflow-runner-smoke.php && php tests/chat-run-control-smoke.php
• composer phpstan
• homeboy --force-hot --allow-local-hot lint --summary --changed-only

AI assistance

• AI assistance: Yes
• Tool(s): OpenCode (GPT-5.5)
• Used for: implemented and tested generic agent run-control for workflows