Remove DEV_FEATURE__SUPER_ROOT_GAMES_MIGRATION

**Claude:**

Track removing `DEV_FEATURE__SUPER_ROOT_GAMES_MIGRATION` after the super root games migration is no longer behind a dev feature.

Cleanup:
- remove the Go/Solidity feature constants and env var handling
- remove the `NO_SUPER_ROOT_GAMES_MIGRATION` CI matrix entry
- remove test-only compatibility branches for the disabled feature path

Search for DEV_FEATURE__SUPER_ROOT_GAMES_MIGRATION and NO_SUPER_ROOT_GAMES_MIGRATION first, then inspect the Go and Solidity constants, environment-variable handling, CI matrix, and test-only compatibility branches they affect. Done means the feature constants and handling, CI entry, and disabled-path branches are removed without breaking the relevant tests or CI.

Written by the indexing model from the issue text.