adapt readme

[Hiepler]

What & why

Type of change

• Bug fix
• New feature
• Refactor / internal
• Docs

How was this verified?

Checklist

• npm run typecheck passes
• npm run lint passes
• npm run test passes
• npm run build passes
• Mock mode still runs with no credentials
• New behavior is covered by tests where it makes sense
• New env flags are documented in .env.example
• The deterministic core stays deterministic (LLM only resolves an already-fixed brief)