validateResponseQuality's streaming-SSE peek only flagged an OpenAI-shape
stream as invalid when it closed WITHOUT ever reaching finish_reason/[DONE]
(#7285 truncation guard). A stream that DOES reach finish_reason: "stop"
but never carries any real content, reasoning, or tool_calls in any chunk
fell through as valid, exactly reproducing the reported content:null /
completion_tokens:0 HTTP 200 for cmd/meta/muse-spark-1.2-contributor.
Add a sibling failover branch for the terminated-but-empty case, mirroring
the existing truncation branch. Tool-calls-only streams are unaffected —
they already short-circuit through the earlier content-detection branch.
Co-authored-by: Markus Hartung <mail@hartmark.se>
cc544db38b