Promote ADR 0007 action-snapshot fixture to main

[tom-snyder]

Summary

• promote the ADR 0007 action-snapshot authoring fixture from dev to main
• keep DesignRNG as the current modelling/schema authority
• publish the public JSON-RPC fixture contract and always-on CI gate

Evidence

• feature PR ADR 0007: publish action-snapshot evidence overlay #26 merged to dev
• exact dev push CI run 29661270639 passed (fixture-contract, web; owner-PAT sidecar job skipped by design)
• independent adversarial review: SHIP

Release order

This promotion follows the project flow: reviewed feature → dev → exact dev CI → main promotion → exact main CI → main back to dev sync.