Done. The assumption register review is in `output/register-note.md`.

**Summary:** Of 20 assumptions, 4 are flagged: 2 with stale reviews (A-09 last reviewed March 2025, A-13 last reviewed June 2025), 1 with no owner (A-16 Merit increase), and 1 with an unsourced change (A-04 Average headcount, which feeds the headcount driver). Five assumptions have changed value since the prior version, all with documented sources except A-04. Before plan lock, Elena Brandt must source the headcount change, an owner must be assigned to merit increase, and the two stale assumptions need review confirmation.