Function scoreBreakingNewsSignificance

Compute a political significance score for a breaking news data payload.

The score is a weighted composite of four dimensions:

• Adopted texts (40 %): more adopted texts → higher legislative impact.
• Affected MEPs (20 %): more MEP updates → wider political scope.
• Legislative stage (30 %): procedures at final reading score higher.
• Committee involvement (10 %): more events → broader institutional engagement.

All inputs are sanitised: null/undefined fields default to zero.