v0.2.1 — Project Core import fix
Bug fix release
Real-world OBF files (CoughDrop exports, the Project Core example from openboardformat.org/examples) use integer button ids, not strings. The v0.2.0 parser threw on these. This release coerces ids to strings and accepts `null` entries in `grid.order` as empty cells.
Cross-checked against the official OBF Ruby gem — the gem accepts whatever the JSON contains because Ruby is dynamically typed. Our string coercion brings parity with what real-world exporters produce.
The Project Core fixture (CC BY-SA, attributed in `NOTICE`) is now part of the test suite.