Records the accepted decision: shard-wiki's native engine uses feature-control via
OpenFeature for per-shard extension activation (availability only, never authz),
provider-pluggable with a LocalProvider standalone default (mirrors the identity
ladder), at the engine layer, consuming the mature feature-control.evaluate slice.
Adds spec/adr/ series + README; hub decision abf7830f recorded.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
