feat(meadows): evolve meadows from forage signals

Summary

• Add a Condukt meadow evolution agent that proposes structured meadow create and update changes from recent work signals.
• Gather forage items, GitHub issues, Grafana alerts, and specs into generic work signals, then validate agent proposals before applying them.
• Configure Oban to run periodic meadow evolution jobs and enqueue unique debounced jobs after forage/spec changes.
• Document current agent use cases, LLM auto-activation, and Tuist’s broader productive software development infrastructure domains.

Testing

• mix format --check-formatted
• mix compile --warnings-as-errors
• mix credo
• mix test