test(server): migrate global bus helper to Effect

[kitlangton]

Summary

• Remove the Promise wrapper around the global bus test helper so callers use the Effect directly.
• Convert the remaining config HTTP API caller to the Effect test runner with scoped temp directory cleanup.

Tests

• bun typecheck
• bun run test test/server/httpapi-config.test.ts test/server/httpapi-instance-context.test.ts