Smaller JSONL fixtures for sqlite-utils import tests

[dKosarevsky]

Could a compact structural fixture help test sqlite-utils imports using --nl and --alter?

ShapeWitness 0.1.0 selects unchanged JSONL rows to cover observed missing fields, nulls, empty collections and mixed types, with source-line provenance and explicit coverage gaps.

A small pilot could use one public fixture: import the full input and the selection, then compare the resulting schema and row-value assertions for retained records. Structural coverage does not guarantee equivalent import behavior. Duplicate-key, ordering and cross-row tests still need separate cases. Original rows are not anonymized.

Code and runnable pytest/importer examples: https://github.com/agent-axiom/shapewitness

Is there an existing import fixture where this would be useful to try?