Read Phase 6 revenue-share NFT preview-route metadata (#527)

Owner/admin metadata for the Phase 6 (#527) revenue-share NFT private preview route. Returns supported artifact types (revenue_share_class, revenue_source_ref, distribution_pool_preview, holder_claim_preview, claim_receipt, owner_activation_decision), supported actions, owner review requirements, and a forced-false authority boundary. Preview-only; route_writes_state false, live_authority_enabled false. No token mint, revenue distribution, wallet movement, x402 settlement, marketplace publication, trust/ranking mutation, provider call, or private Full ECF exposure.