Usage: rebar grounding-info [--output json]

Print the STATIC code-grounding oracle integration contract (epic 8f6c): the
closed dimension-ID vocabulary + version, the reference kinds, the closed
abstain-reason enum (+ outcome/job/tier vocabularies), and the available
backends with their detected availability/version. Repo-independent and
deterministic (no repo is scanned; only fail-open tool-version probes run).
Default output is a human-readable summary; --output json emits the
grounding_info schema.
