v2.5.2

• Spec v3.5.1 conformance (SPEC 5, score-rounding errata). SPEC 5 now pins the graph score two-decimal wire form to round-half-to-even on the exact IEEE-754 double, resolving a midpoint divergence in the JavaScript and Kotlin SDKs. This SDK's f"{score:.2f}" formatter already rounds half-to-even, so there is no behavior change; re-verified against the new graph-encode/004_score_midpoint_rounding conformance fixture.

Part of spec v3.5.1.