release: bump version 0.8.3 -> 0.8.4

Ships worker-settable catalog source_url + per-schema tags (declarative Catalog
descriptor) for vgi-lint metadata. Function tags were already supported.

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

Author: rustyconover

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "vgi-python"
-version = "0.8.3"
+version = "0.8.4"
 description = "Vector Gateway Interface - Connect DuckDB to external programs via Apache Arrow"
 readme = "README.md"
 keywords = [