frontend/itl_expr Design

The package parses the ITF1788 line language into typed cases, then dispatches supported operations to BallFloat and BallFloatDecorated. Expected interval, boolean, overlap, numeric, and decoration results use operation-specific comparators. Summaries are folded through the shared conformance model.

Unsupported operation, arity, or expected-value forms remain explicit dispositions. The package does not claim full IEEE 1788 support, read files, or choose strict phases; testdata/interval/README.md and tooling define the gate.