Module churn 

Churn analyses per spec §1.1:

• abs-churn: by date (added/deleted/commits)
• author-churn: by canonical_author (added/deleted/commits)
• entity-churn: by path (added/deleted/commits)

Research basis: see docs/research-foundations.md entry “churn” (Nagappan & Ball, ICSE 2005 — relative code churn predicts system defect density; foundational input to nearly every downstream behavioural signal).

Structs

AbsChurnRow

AuthorChurnRow

EntityChurnRow

Functions

run_abs_churn

run_author_churn

run_entity_churn