Configure validation in project dev #1525

User story

As a dev, I want to control how validation runs from project dev, so I understand the checks and isolation trade-offs before running them.

This story addresses the hidden tool-selection and copy-mode friction I saw during my tour.

Scope

Following the Validation/Config mockups:

• Select tools using existing --only / --exclude behavior.
• Configure validation copy behavior.
• Show validation freshness.
• Mark results stale and offer rerun when relevant settings change.

Acceptance criteria

• TUI options map to existing CLI semantics.
• Copy/isolation behavior is explicit.
• Changed settings cannot leave an old result looking current.

Readiness checklist

• Acceptance criteria are clearly defined.
• Backward compatibility impact addressed.
• Documentation written.
• Tests added or adjusted accordingly.