* Add local OpenAI-compatible model discovery to /model
* Guard local OpenAI model discovery from Codex routing
* Preserve remote OpenAI Codex alias behavior
On Windows, shells can set OPENAI_BASE_URL to the literal string
"undefined" when the variable is referenced without quotes while unset.
The nullish-coalescing operator (??) does not catch this because
"undefined" is a truthy string, causing resolveProviderRequest() to
treat it as a real base URL. This broke the Codex transport check:
(!rawBaseUrl && isCodexAlias(model)) evaluated as (false || true) = false
so the transport was incorrectly set to chat_completions (issue #336).
Fix: introduce asEnvUrl() which trims the value and rejects both empty
strings and the sentinel string "undefined". Use it for all three
rawBaseUrl sources (options.baseUrl, OPENAI_BASE_URL, OPENAI_API_BASE).
Tests: add three new cases to the 'Codex provider config' describe block
covering the empty-string, "undefined"-string, and options-override
scenarios. Also add beforeEach/afterEach guards so individual tests
cannot contaminate each other via env var state.
Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>
