Add temporary containment control ledger gates

[malb200710-dev]

Closes #2243

Summary

• adds a temporary containment control ledger gate to the containment skill
• requires owner, approval, scope, start time, expiry/review time, effectiveness evidence, business-impact evidence, and removal plan for emergency controls
• adds severity guidance for stale temporary controls and containment exceptions
• updates the output format with a control-ledger table

Validation

• content assertions for version bump, ledger section, owner/expiry/removal fields, severity guidance, and output table