Prepare 2.6.3 release: set version to 2.6.3

Drop the .dev4 suffix from the package version in pyproject.toml so that
pushing the 2.6.3 tag publishes a final release to PyPI. The latest feature
PRs (libigl bump + new bindings) will be merged into main and incorporated
here before tagging.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: Horde

pyproject.toml

@@ -13,7 +13,7 @@ build-backend = "scikit_build_core.build"
 
 [project]
 name = "libigl"
-version = "2.6.3.dev5"
+version = "2.6.3"
 description = "libigl: A simple C++ geometry processing library"
 readme = "README.md"
 requires-python = ">=3.8"