test: full precision 명령의 Ref 투영 경계를 고정한다

tools/integration-tests/src/turn-differential/legacyNumericProjection.ts

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+import type { CanonicalTurnSnapshot } from './canonical.js';
+
+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);
+};
+
+/**
+ * Test-only projection for a MariaDB FLOAT read through the Ref PHP service.
+ * Core product state intentionally keeps JavaScript/PostgreSQL precision; this
+ * oracle is only used to prove that an explicitly enumerated raw difference is
+ * caused by Ref's binary32 write and six-significant-digit read boundary.
+ */
+export const projectRefFloatRead = (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 interface RefFloatSnapshotProjection {
+    cityTrust?: boolean;
+    nationTech?: boolean;
+}
+
+const projectField = (row: Record<string, unknown>, field: string): Record<string, unknown> => {
+    const value = row[field];
+    if (typeof value !== 'number' || !Number.isFinite(value)) {
+        return row;
+    }
+    return { ...row, [field]: projectRefFloatRead(value) };
+};
+
+export const projectSnapshotThroughRefFloatRead = (
+    snapshot: CanonicalTurnSnapshot,
+    projection: RefFloatSnapshotProjection
+): CanonicalTurnSnapshot => ({
+    ...snapshot,
+    cities: projection.cityTrust ? snapshot.cities.map((city) => projectField(city, 'trust')) : snapshot.cities,
+    nations: projection.nationTech ? snapshot.nations.map((nation) => projectField(nation, 'tech')) : snapshot.nations,
+});