Purpose: record scenarios moved out of the active benchmark set and why.

Scenarios are moved out of the active corpus when they do not improve benchmark value, typically due to high redundancy or overlapping narrative role.

The historical dropped set is kept in corpus_dropped_v1/ for traceability.

Main reasons:

• high pairwise similarity with active scenarios,
• duplicated narrative role in the same family/regime,
• low marginal contribution to diversity goals.

Dropped scenarios are not deleted from project history; they remain documented as part of corpus evolution.