Add OpenAI responses mode and custom auth headers (#906)

* Add OpenAI profile responses and custom auth header support

* Fix knowledge graph config reference in query loop

* Address OpenAI profile review edge cases

* Remove unused getGlobalConfig import

Delete an unused import of getGlobalConfig from src/query.ts. This cleans up dead code and avoids unused-import lint warnings; no functional behavior changes.

* Address follow-up OpenAI profile review comments

* Refine OpenAI responses auth review fixes

* Fix custom auth header default scheme

src/utils/providerSecrets.ts

@@ -1,5 +1,6 @@
 const SECRET_ENV_KEYS = [
   'OPENAI_API_KEY',
+  'OPENAI_AUTH_HEADER_VALUE',
   'CODEX_API_KEY',
   'GEMINI_API_KEY',
   'GOOGLE_API_KEY',