v0.5.1

Precision tightenings from real-world field validation: the skill was applied to 200 real repos (50 each Python/TS/JS/Robot, #99) and held up - the gaps were implicit look-alike exemptions, now explicit so an LLM does not over-fire. reference.md adds: non-assert oracles (helper/fluent matchers, pytest runner results, throwing Testing-Library queries, hand-rolled throw/assert, type-level assertions), a sharper mock-vs-SUT boundary (S12/S16/S5), guard exemptions (expect.assertions, pytest.raises message), workshop fixtures, and a contract-scoped Robot file-role rule. SKILL.md generalizes the finding header to {code} ({J}) and adds the C9/C28/S17 tie-break. No new or removed codes (121). See CHANGELOG.md.