wickworks v0.3.1 — Bar.ge=0 + doc surface trim

- Bar.tickVolume / realVolume: Pydantic now enforces ge=0 to match
  the schema's `minimum: 0` (negatives previously slipped through to
  volume indicators).
- schema.json + README scrubbed of alias-doc noise; only the
  canonical camelCase wire shape is documented. Runtime still accepts
  snake_case as an undocumented convenience.

No API shape changes. Regression tests added.