LLM/output stage codes outside STATUS_CODE_MAP were passed through
silently with an empty nextStage - undetectable drift between the
prompt output code set and the endpoint mapping table.
- endpoints: _stage_label / _warn_unknown_stage_code helpers; both
streaming and non-streaming paths emit a warning with sessionId,
clientMode, raw and normalized codes when the label lookup misses
(transparency behavior unchanged: code passes through, label empty)
- known codes and covered internal normalizations (e.g. 2020->0002)
stay silent; the warning fires on the normalized value
Verified: 229 unit tests (4 new monitoring tests)
Eric Wang
11131885a6