feat: create same FableCodex workflow for Opencode also"

[chintu79]

Problem

I don't have any idea of this repo, i just used it and it works great. Need same for Opencode ASAP.

Proposal

Need same for Opencode ASAP.

Evidence or examples

No response

Boundary check

• This does not claim to reproduce Fable 5 model capability.
• This does not require committing credentials or private prompt text.