Symmetric with cmd/rlp-import. Thin HTTP client that:
1. Idempotency precheck reads <output-file>.sentinel on the local PVC
and short-circuits when Status=done + range matches — luxd is never
contacted in the warm-cron case.
2. Health-probes ${LuxdRPC}/ext/health (30s cap).
3. POSTs admin_exportChain via /ext/bc/${chain}/rpc with KMS_AUTH_TOKEN
bearer auth (same env-var contract as rlp-import).
4. Maps Status → exit code:
ok | noop → 0
interrupted → 4 (operator re-runs with from-height=HighestExported+1)
bad input → 1
luxd unreach → 2
admin RPC err → 3
Lives in the cmd/ nested module per the existing rlp-import precedent.
Builds with GOWORK=off; Makefile target `make rlp-export` does this for you.
Tests cover: flag parsing, "latest" resolution, all four idempotency
fall-through branches, happy path + noop + interrupted server responses,
luxd unreachable, admin RPC error, KMS_AUTH_TOKEN bearer header
plumbing. 14 tests, all green.
Symmetric Makefile additions: `make rlp-export`, `make rlp-import`,
`make cmds`, `make test-rlp-export`.