Assertion-block schemas

Canonical conformance claims use three historical object names: assertions, expect, and expected. They are executable contract data, not free-form fixture metadata.

schemas/assertion-blocks.json gives every such object a fail-closed Draft 2020-12 schema. Each route is identified by its fixture-relative path and a JSON pointer whose array indexes are normalized to *. Route schemas:

• reject unknown keys with additionalProperties: false;
• require every key present in all examples at that route;
• validate scalar, array, object, and nested value shapes;
• cover every fixture area, including families without a whole-fixture schema;
• are checked in both directions, so an unvalidated block and a stale unused schema route both fail.

The file is generated from reviewed corpus state, but it is intentionally checked in. A fixture edit therefore has to carry a visible schema diff:

python3 scripts/gen_assertion_block_schema.py

make check runs the generator in --check mode and mutation-checks unknown keys, missing required keys, wrong value types, and unknown fixture routes. This guard complements binding-side read/assert ledgers: JSON Schema constrains what a fixture may say, while the runtime ledgers prove a binding actually consumed and asserted what the fixture said.