Phase B: audit presets.ts envAny:OPENAI_CODEX_ACCESS_TOKEN

[samxu01]

Follow-up to ADR-014. `backend/routes/registry/presets.ts:128` references `OPENAI_CODEX_ACCESS_TOKEN` and `OPENAI_CODEX_REFRESH_TOKEN` in an `envAny` array — appears to be in agent preset auth config.

Need to understand:

1. What is `envAny` used for in preset definitions?
2. Does any current agent preset actually read it (vs. inherit from runtime-provisioned LiteLLM virtual key)?
3. Safe to drop, or part of fallback contract?

This is the smallest of the Phase B issues but the least understood — investigate before yanking.

Related: ADR-014, PR #370.