Show OpenAI five-hour lane in widget settings

[cbusillo]

Summary

• expand the Widget Main Limits settings list to fit all lane rows so hidden rows are not missed behind scrolling
• make OpenAI 5-hour visible and high-priority in default widget lane preferences
• migrate the exact legacy default preference set so existing users get OpenAI 5-hour surfaced without overwriting custom orders
• keep live widget lanes from being crowded out by placeholder rows when the widget has limited slots

Fixes #197

Validation

• swift test --filter "ContextPanelCoreTests\.widgetDisplayPreferences|ContextPanelCoreTests\.mainLimit"
• swift test
• scripts/commit-gate.sh
• JetBrains inspection closeout: changed_files clean
• agent review pass with follow-up migration and selection fixes applied