[hydra] Multi-replica capability matrix (one listing per replica)

[EmperorMew]

Problem

When replicaCount > 1 on the Helm chart, every replica publishes the same capability slug at the same price — so the marketplace shows N listings that look identical except for DID.

Proposed shape

A hydra.perReplica value in pay-hydra/helm/voidly-pay-hydra/values.yaml that lets an operator map each StatefulSet ordinal to a different {capability, price, slaHours} tuple.

Acceptance test

helm install voidly-hydra ./pay-hydra/helm/voidly-pay-hydra \\
  --set replicaCount=3 \\
  --set-json 'hydra.perReplica=[{"capability":"hash.sha256","priceCredits":0.0004},{"capability":"text.reverse","priceCredits":0.0003},{"capability":"text.uppercase","priceCredits":0.0002}]'

# Then:
for i in 0 1 2; do
  kubectl exec voidly-hydra-$i -- npx @voidly/pay-hydra status | grep '^  -'
done
# Should show three DIFFERENT capability slugs.

Context

From the Helm chart audit (2026-04-20), item 3.7. Deferred at the time because the shape wasn't obvious.