- Preserve API key entries with empty `api_key` when `base_url` is configured, and extend config dedupe/ID logic to include base URL, proxy, prefix, and headers so identities are stable.
- Update config/auth handling so `auth_kind=apikey` is treated as config API-key auth even without an `api_key` field, enabling base_url-only credential records.
- Ensure Gemini/Codex/XAI request path clears `Authorization`/provider auth headers when token is empty to avoid leaking unrelated auth state.
- Propagate request headers into custom-header resolution for OpenAI/Gemini/XAI/Codex execution and websocket flows.
- Resolve auth `header:` values like `$ABC` from incoming request headers at request time and omit headers when no value is available.
- Add documentation for the dynamic custom-header behavior in `config.example.yaml`.
Closes: #5053
- Removed deprecated interceptor and executor-related methods, including `callRequestInterceptor`, `callResponseInterceptor`, and `callStreamChunkInterceptor`.
- Consolidated unused logic and pruned redundant imports to streamline `adapters.go`.
- No functional changes.
