fix: align scenario 2400 monthly parity

packages/logic/src/compat/legacyFloat.ts

@@ -3,8 +3,27 @@
 // command/battle update, so both boundaries are part of the game state.
 export const toLegacyStoredFloat = (value: number): number => Math.fround(value);
 
-export const readLegacyStoredFloat = (value: number): number =>
-    Number(Math.fround(value).toPrecision(6));
+const roundHalfEven = (value: number): number => {
+    const lower = Math.floor(value);
+    const fraction = value - lower;
+    const tolerance = Number.EPSILON * Math.max(1, Math.abs(value)) * 4;
+    if (Math.abs(fraction - 0.5) <= tolerance) {
+        return lower % 2 === 0 ? lower : lower + 1;
+    }
+    return Math.round(value);
+};
+
+export const readLegacyStoredFloat = (value: number): number => {
+    const stored = Math.fround(value);
+    if (!Number.isFinite(stored) || stored === 0) {
+        return stored;
+    }
+    const sign = stored < 0 ? -1 : 1;
+    const absolute = Math.abs(stored);
+    const exponent = Math.floor(Math.log10(absolute));
+    const scale = 10 ** (5 - exponent);
+    return sign * (roundHalfEven(absolute * scale) / scale);
+};
 
 export const addLegacyStoredFloat = (current: number, delta: number): number =>
     toLegacyStoredFloat(readLegacyStoredFloat(current) + delta);