[maintainer] Ingest root-vs-alpha stake split for validators

[JSONbored]

dTAO validators hold both root (netuid 0 / TAO) and per-subnet alpha stake; the directory should show the split. The neurons tier stores a single stake_tao per membership row with no root/alpha decomposition, so this needs new ingestion + schema modelling of the two stake legs — architectural/infra, maintainer-only.

Deliverables

• Model the root vs alpha stake legs (schema migration adding root_stake_tao / alpha_stake_tao, or a derived netuid-0 aggregation rule) with a documented decision
• Extend the refresh cron/staging path to populate both legs from the upstream source
• Expose root_stake_tao / alpha_stake_tao (and a combined view) in buildGlobalValidatorEntry + /api/v1/validators + contracts + OpenAPI
• Add a root/alpha stake split display to the per-validator detail page once the fields ship
• Tests covering the split math + nullish legs

References

• repo/src/metagraph-neurons.mjs:9 (stake_tao is a single value)
• repo/src/metagraph-neurons.mjs:272 (per-subnet stake push, no root/alpha split)
• repo/migrations/ (add contiguous NNNN_*.sql)

---

size: M · maintainer-only (owner)

[linear-code]

JSO-2088