feat(rpc,bench): emit per-pod URLs in up envelopes from SND status

[bdchatham]

Summary

Closes #118. After rpc up --apply and bench up --apply, poll the SND's status.perPodServices (published by sei-k8s-controller#158) and emit endpoints.perPod[] with dial-ready URLs:

http://<pod>.<namespace>.svc:<evmHttp>
ws://<pod>.<namespace>.svc:<evmWs>

This closes the loop on platform's nightly JSONPath workaround (sei-protocol/platform#334) — consumers that need per-pod connectivity (seiload's WebSocket block collector, future qa harness) can read .data.endpoints.perPod[].evmWs from the standard envelope instead of re-implementing label-and-filter Service discovery.

Envelope shape

Before:

{
  "data": {
    "endpoints": {
      "tendermintRpc": ["http://...-rpc-primary-internal..."],
      "evmJsonRpc":    ["http://...-rpc-primary-internal..."]
    }
  }
}

After (with --apply and a controller publishing the new field):

{
  "data": {
    "endpoints": {
      "tendermintRpc": ["http://...-rpc-primary-internal..."],
      "evmJsonRpc":    ["http://...-rpc-primary-internal..."],
      "perPod": [
        {
          "name": "pacific-1-rpc-primary-0",
          "evmJsonRpc": "http://pacific-1-rpc-primary-0.nightly.svc:8545",
          "evmWs":      "ws://pacific-1-rpc-primary-0.nightly.svc:8546"
        },
        { "name": "pacific-1-rpc-primary-1", ... }
      ]
    }
  }
}

perPod is omitempty. Dry-run never populates it; controllers without the new status field also produce an empty result.

Implementation notes

• New kube.GetSND returns *unstructured.Unstructured. Dynamic client preserves the architectural constraint that seictl never imports the typed sei-k8s-controller API surface.
• perPodPoller is dependency-injected for tests. Production polls every 1s up to 30s, then emits a stderr warning + perPod omitted; the apply itself is unaffected.
• PerPod lives inside the existing Endpoints struct rather than as a sibling on the result types — keeps URL handles under one umbrella and applies uniformly to chain/rpc/bench (chain currently doesn't poll, so it stays empty there).
• Order in the envelope mirrors the controller's order (sorted by ordinal in populatePerPodServices); the parser does not re-sort.

Test plan

• go test ./cluster/... — green
• Parser tests cover: nil unstructured, missing status, missing perPodServices, controller-ordered output, malformed entries dropped, partial result returned for poller to retry.
• Wiring tests cover: rpc up --apply invokes the poller with the right SND name + replicas; dry-run skips it; bench up --apply queries ${chainID}-rpc with sizeProfile.RPC replicas.
• Live verify post-merge: seictl rpc up --apply -o json | jq '.data.endpoints.perPod[].evmWs' against harbor.
• Follow-up: open platform PR replacing the JSONPath block in k8s_nightly.yml with a jq over the new envelope (after a new seictl release ships).

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