P3: odd cents split the same running way everywhere (defect 17, D-38)

Members' shares of earnings are split cumulatively by largest remainder in
the closes, the members' equity statement, the K-1 worksheet and the
viewer, so a member's capital on a given day never moves by a cent when its
month is later closed. Old closes replay as they were; the first P3 close
carries any true-up. Feature members_cumulative. Kani and Lean proofs of
the bounded drift; bookspec examples.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01T3gXMVt7XJPi6ens1or9Dj

crates/ledger-core/Cargo.toml

@@ -22,6 +22,8 @@ workspace = true
 [dev-dependencies]
 criterion = "0.8.2"
 proptest = "1"
+# bookspec examples are TOML (tests/bookspec.rs).
+toml = "1"
 
 [[bench]]
 name = "books"