wickworks v0.3.0 — primitives-only purification

Breaking: removes divergences + divTrends outputs and the entire
signals/ package. Wickworks now emits only raw indicators, SMC
structural facts, and summaries. Derived signals (divergence,
crossovers, golden/death crosses) are the consumer's job.

Includes:
- README rewritten with primitives-only contract
- schema.json published as release artifact
- registry trimmed, signals/ package deleted
- tests adjusted for new shape