aco.lake.DuckLakeContext: the concrete lake context for the M3
decision (#512). Subclasses DuckDBContext — load/save are inherited
untouched; only the connection wiring differs (ducklake+httpfs
extensions, S3 secret for RustFS, ATTACH the catalog, USE it as the
default database so schema.table refs resolve in the lake). Postgres
DSN for multi-writer prod, plain file path for dev/tests. Explicit
close() added to the context family (releases locks/attachments).
Pilot: dev/scripts/publish_opps_to_lake.py reads the OPPS tables from
the replica and writes them through Context.save(mode=replace). Run
against prod (postgres catalog db 'ducklake' + RustFS): addendum_b
219,665 rows in 2.6s, apc_weight 7,776, skin_sub_addendum_b 2,520 —
all read-back verified through Context.load.
Config: stack.toml [lake.ducklake] (catalog DSN sans password, data
path, s3 endpoint). CI: ducklake added to the duckdb extension
preinstall (same xdist install race class as #515). 6 new tests use a
file catalog + local data path — same code paths, no services needed.