Bump minimum black version to 26.1.0

Black 26.1.0 introduced new formatting rules that affect this codebase.
Pin to >=26.1.0 to ensure consistent formatting across all environments.
Black 26.1.0 requires Python >=3.10 which matches this project's minimum.

Author: claude

pyproject.toml

@@ -33,7 +33,7 @@ dependencies = [
 
 [dependency-groups]
 dev = [
-    "black>=24.1.1",
+    "black>=26.1.0",
     "cogapp",
     "hypothesis",
     "pytest",