Case-style rewording for migrated test directives

[omridevk]

Context

Issue #13 shipped ::: test body directives and migrated the four toolchain modules. The migrated vectors preserve fixture vocabulary, but they read like serialized unit tests rather than concise English examples of language behavior.

This is the deferred derivation phase from docs/specs/2026-07-25-remove-frontmatter-tests-plan.md, updated for the shipped directive and canonical-document architecture in docs/specs/2026-07-28-test-directives-v1.md.

Problem

Names, given, and expect values currently expose implementation-shaped fixture terms. They are exact and machine-readable, but they are not yet good author-facing cases. Mechanical migration preserved meaning correctly; it did not perform the semantic rewriting that turns fixtures into readable language examples.

Scope

• Define the derivation contract that proposes case-style rewrites from prompt prose without seeing generated implementation.
• Rewrite migrated vectors into clear, behavior-named examples while preserving their pinned meaning.
• Keep author-stated directive cases distinct from machine-proposed cases until explicit sanction.
• Record prompt-line provenance and canonical diffs for every proposed case change.
• Keep frontmatter tests: legal and empty during this phase.

Acceptance criteria

• Migrated cases read as concise English behavior examples rather than serialized test fixtures.
• Every rewrite is meaning-preserving, reviewable as a canonical case diff, and explicitly sanctioned.
• Derivation uses prompt prose and directive data only, never generated code or the code-writing conversation.
• The canonical napl q document exposes the resulting cases without another representation or corpus concept.
• Conformance pins proposal validation, sanctioning, rejection, and unchanged-input behavior.

References

• Tests-removal implementation (::: test directives) #13
• docs/specs/2026-07-25-remove-frontmatter-tests-plan.md
• docs/specs/2026-07-28-test-directives-v1.md