Snippets were plain Python dicts — marimo expects actual notebook files (marimo.App with @app.cell). Rewrote all 10 as proper marimo notebooks that load_app() can parse. Disabled include_default_snippets — only our project snippets show. 10 snippets: duckdb, trino, bib, nessie, s3-obstore, chart-bar, chart-line, query-demographics, query-schema, query-pmpm. refs #75