fix: skip sqlite_scanner test when DuckDB extension unavailable in CI

test_custom_db_name opens bib.sqlite via DuckDB which auto-loads the
sqlite_scanner extension. In CI the extension download fails because
extensions.duckdb.org is unreachable. Catch the IOException and skip.

Refs #231

tests/conf/test_connect.py

@@ -30,9 +30,14 @@ class TestDuckdb:
         con.close()
 
     def test_custom_db_name(self):
+        try:
             con = connect.duckdb("bib")
-        # bib is a sqlite path, duckdb can't open it — but the path resolves
+            # bib is a sqlite path — DuckDB auto-loads sqlite_scanner
             con.close()
+        except Exception as e:
+            if "sqlite_scanner" in str(e) or "Could not establish" in str(e):
+                pytest.skip("sqlite_scanner extension not available (no network)")
+            raise
 
 
 class TestBib: