docs: both api keys, example model gpt-5.4-nano

examples/folio/README.md

@@ -81,19 +81,21 @@ Traces land in `./sanderling/runs/<timestamp>/`.
 ## Run with the LLM action backend
 
 `sanderling/spec-llm.ts` reuses the same properties and login setup but swaps the
-seeded fuzzer for `llm({ model })`: an OpenRouter vision model chooses which of
-the already-enumerated candidates to act on each step, from the screenshot.
+seeded fuzzer for `llm({ model })`: a vision model chooses which of the
+already-enumerated candidates to act on each step, from the screenshot.
 
 ```sh
-export OPENROUTER_API_KEY=sk-or-...
+export OPENROUTER_API_KEY=sk-or-...   # or OPENAI_API_KEY=sk-... for OpenAI direct
 sanderling test --spec sanderling/spec-llm.ts --bundle-id app.folio --duration 2m
 ```
 
-The model must support image input **and** strict `json_schema` structured
-outputs (e.g. `openai/gpt-4o`); edit the `model` string in `spec-llm.ts` to pick
-another. Each step is one multimodal call, so keep the duration / step budget
-modest. The trace records the model's reasoning and `source: "llm"` on each
-chosen action, so the replay UI shows why each pick was made.
+OpenRouter wins when both keys are set. With a plain OpenAI key, drop the vendor
+prefix from the model id in `spec-llm.ts` (`gpt-5.4-nano`, not
+`openai/gpt-5.4-nano`). The model must support image input **and** strict
+`json_schema` structured outputs. Each step is one multimodal call, so keep the
+duration / step budget modest. The trace records the model's reasoning and
+`source: "llm"` on each chosen action, so the replay UI shows why each pick was
+made.
 
 ## Run a sanderling test (iOS)