v0.5.1

The .pio.json payload schema is declared and versioned independently of the envelope (payload_schema, payload_schema_version; envelope schema_version 0.1.1). Payload rows carry stable uid identities. Operating point updates resolve by identity, a present row is a consistency check, and unknown identities are rejected at materialization and by validation. Packages from 0.5.0 read unchanged.

Python table dicts expose uid. No C ABI signature changes. Docs are restructured and served at https://powerio.dev.

Details in CHANGELOG.md.