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/src/money.rs

@@ -57,6 +57,18 @@ impl Currency {
         }
     }
 
+    /// The decimal places a share of an amount in this currency is split
+    /// to (members' shares of earnings, periods::allocate_cumulative): its
+    /// minor units (cents, whole yen, thousandths of a dinar), or, for a
+    /// code ISO 4217 gives none (gold, SDRs), the most a line may carry
+    /// (kernel::MAX_LINE_SCALE). Every posted amount is then a whole number
+    /// of the unit split to, so no member's running share is ever a unit
+    /// from exact (rules.md B-13); split to cents, a finer amount's
+    /// leftover fraction would all go to one member.
+    pub fn allocation_places(&self) -> u32 {
+        self.minor_units().unwrap_or(crate::kernel::MAX_LINE_SCALE)
+    }
+
     /// The three-letter code, e.g. `"USD"`.
     pub fn code(&self) -> &str {
         std::str::from_utf8(&self.0).expect("currency codes are ASCII by construction")