Document host-catalog selection for Fable reviews - #1083

Why

A saved Fable model name can disappear from the host provider’s catalog and refuse before a review prompt is sent. The workflow guide needs to explain how to select an available model and retain that failure evidence.

What changes

Before: the guide required provider/model attribution but left model selection and pre-prompt refusal handling unspecified.

After: select Fable from the host’s advertised catalog, prefer its fable alias when available, and record the exact provider and resolved model. Preserve a refused selection and confirm that no prompt was sent before correcting the configuration; automatic retries stay disabled.

How to verify it

• git diff --check passes.
• Reviewed the prose against the existing independent-review and fallback rules. This changes one Markdown guide and contains no executable blocks.

Scope

• examples/adversarial-implementation/README.md only.

Scope confirmation

• Every changed file supports the purpose described above.
• Unrelated cleanup and formatting changes are excluded.
• Generated or mechanical changes are clearly identified: none.
• The description matches the final diff and verification.