release: 0.27.0 — the landing page reads the catalog over the protocol

Drops the describe.json producer (462 lines), the vendored JSON contract, and
the cross-language conformance harness: the shared landing page now speaks the
VGI protocol through the browser client build served at {prefix}/vgi-client.js.

Adds attach-option `required`, enforced at catalog_attach.

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

Author: rustyconover

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "vgi-python"
-version = "0.26.0"
+version = "0.27.0"
 description = "Vector Gateway Interface - Connect DuckDB to external programs via Apache Arrow"
 readme = "README.md"
 keywords = [