By: Tom Sydney Kerckhove <syd@cs-syd.eu>
Add structural invariant tests for register blocks For every single-currency register test case, assert: - Running average at block i equals runningTotal / i - Running total equals cumulative sum of block totals - Block titles are in strictly increasing order - Empty blocks have zero total and same running total as previous These tests verify the register logic independently of golden text output, catching bugs even when golden files are reset.