## Summary - keep preview-overridable Compose values as direct references instead of eager `:-` defaults - move local planner/model defaults into `.env.example` - guard the Coolify late-binding contract with a focused YAML test and document the precedence rule

## Root cause Coolify materializes default-bearing service environment entries from production before attaching the preview `.env`. The explicit production value then overrides the correct preview value.

## Verification - `bun test` - `bun run types` - `bun run ci` - `docker compose -f compose.yaml config --format json` with preview-specific values - independent review: no remaining findings