v0.19.0

Added

• Approval grant-rate telemetry — operational scorecard now tracks approvals_granted, approvals_denied, and derived approval_grant_rate (approval-fatigue signal). export_scorecard() emits cp.approvals_granted, cp.approvals_denied, cp.approval_grant_rate.
• AgentMetadata.is_capable(action) — single source of truth for an agent's effective authority. Establishes and documents the "delegation does not elevate trust" invariant.
• Per-session agent revocation primitive — new AgentSessionGuard (revoke / reinstate / is_revoked) backed by agent_session_revocations table, emitting state-bearing AGENT_REVOKED / AGENT_REINSTATED events.

Fixed

• Gateway classes exposed on facades since 0.18.0 are now exported from agent_control_plane.