Robinhood Chain Vague 1: weekend drift + arb latency + subsidy tracker

[Flotapponnier]

Summary

• 079 tokenized-stock-weekend-drift: max deviation per closed session (72h window aggregated per weekend), pure PromQL on existing tsp_deviation_bps series. Zero new probe
• 080 tokenized-stock-arb-latency: seconds until pool converges to 20bps of ref after a 50bps 1-min move. New in-process event tracker in tokenized-stock-peg harness, emits tsp_arb_latency_seconds histogram + tsp_arb_event_total counter. Regular hours only, in-flight events at session end close as still_open
• 081 robinhood-subsidy: countdown to 2026-09-29 + estimated chain-side USD cost since launch. Small new harness reading Blockscout /stats + /charts/transactions + RPC gasPrice, all keyless. Deliberately labeled "chain-side" not "user fees" to avoid contradicting growthepie's ~$0 fees_paid_by_users during the subsidy
• All 3 staging gated
• Verification agent caught two would-be blockers before ship: /charts/gas-used is 400 on this Blockscout instance (parser switched to /charts/transactions), and the burn narrative had to be re-labeled to not clash with growthepie