Bump to v1.3.1 and refresh benchmark artifacts

CHANGELOG.md

@@ -7,6 +7,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [1.3.1] - 2026-05-14
+
 ### Changed
 - **Lazy `VectorVariable` fast paths**: LP extraction, bounds handling, and solver setup now preserve vector-backed metadata longer instead of forcing immediate scalar `Variable` materialization.
 - **Single-vector NLP cold-start path**: Unconstrained `VectorVariable` objectives such as `x.dot(x) - x.sum()` now compile through a contiguous vector layout, reuse vector-backed solver metadata, and avoid first-solve scalar materialization on the hot path.

benchmarks/results/benchmark_metadata.json

@@ -3,11 +3,11 @@
   "cpu_count": 2,
   "machine": "x86_64",
   "numpy_version": "2.3.5",
-  "optyx_version": "1.3.0",
+  "optyx_version": "1.3.1",
   "platform": "Linux-6.8.0-1044-azure-x86_64-with-glibc2.39",
   "processor": "x86_64",
   "python_implementation": "CPython",
   "python_version": "3.12.1",
   "scipy_version": "1.16.3",
-  "timestamp_utc": "2026-05-14T14:42:29.831269+00:00"
+  "timestamp_utc": "2026-05-14T15:39:50.351535+00:00"
 }