The append mode used to feed chunks as successive conversation turns with
the context carried over. The model then copied the previous turn's text
verbatim instead of transcribing the new audio, so a continuous video
kept showing the same sentence forever. Transcribe each chunk
independently instead, matching sglang's segment streaming mode for
Qwen3-ASR; the fixed mode also stays flat at RTF 0.24 versus 0.57-1.08
for the incremental mode.
修复追加式的一个真 bug：原先把各段接成「携带上文的对话轮」，模型会抄上
一轮的文本 —— 连续视频里字幕永远重复同一句。改为每段独立转写（对应
sglang 给 Qwen3-ASR 的 segment 流式模式），内容随之正确变化；成本仍保持
平坦，RTF 0.24，而增量模式是 0.57~1.08。
blumia
6d64987d64