refactor(bayn): align test Effect idioms

[gregkonush]

Summary

• Aligns test configuration, schemas, JSON, errors, and async primitives with Effect APIs.
• Keeps this native stack layer independently reviewable at 579 changed lines.
• Bases directly on codex/bayn-effect-tsgo-runtime-composition so GitHub shows only this layer.

Related Issues

None

Testing

• bunx tsc --noEmit --project services/bayn/tsconfig.json
• bun run lint
• bun run lint:oxlint
• bun run lint:oxlint:type
• bun run build
• Focused tests for the touched subsystem were run while constructing the layer.

Breaking Changes

None

Checklist

• Testing section documents the exact validation performed.
• Screenshots are not applicable and Breaking Changes is filled in.
• Documentation and follow-ups are unchanged or represented by later stack layers.

[chatgpt-codex-connector]

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