chore: bump to v2.6.3

Version bump for release. uv.lock re-locked in the same commit because it
embeds the project's own version, and a bare pyproject bump leaves the two
files disagreeing with nothing to catch it.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: vvillait88

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "agentscore-py"
-version = "2.6.2"
+version = "2.6.3"
 description = "Python client for the AgentScore APIs"
 readme = "README.md"
 license = "MIT"