fix(deploy): seal with staging trust root on the staging gateway

The staging validator verifies bundles against config/challenges.staging.toml
(design 2000 bps) but the gateway kept sealing with the prod root (design
0 bps): design weight never surfaced and every coordination compare failed
with emission share mismatch (D23). Mount the staging root on the gateway too.

Author: echobt

deploy/compose/env-staging.yml

@@ -38,6 +38,11 @@ services:
       - "80:8080"
     volumes:
       - ./deploy/secrets/wallets:/run/base/wallets:ro
+      # The sealer must sign with the same staging trust root the validator
+      # verifies against (design 2000 bps), or /v1/weights/latest never shows
+      # design weight and the validator flags emission share mismatch (D23).
+      - ./config/challenges.staging.toml:/etc/base/config/challenges.toml:ro
+      - ./config/challenges.staging.toml.sig:/etc/base/config/challenges.toml.sig:ro
   prism-challenge:
     environment:
       BASE_CHAIN_ENDPOINT: "wss://test.chain.opentensor.ai:443"