- Initialize `util.SessionIDResolver` to resolve session IDs from request contexts, metadata, and headers.
- Ensure canonical session metadata is injected into execution options across execution flows.
- Propagate session context in executors to support `$CPA-SESSION-ID` expansion in custom headers.
- Sync cleared or updated session identities back to execution contexts during conductor execution.
Closes: #5690
- Propagate request headers into custom-header resolution for OpenAI/Gemini/XAI/Codex execution and websocket flows.
- Resolve auth `header:` values like `$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