sembench 0.2.3

0.2.3

• The system turn a manifest row asks for is now sent. Rows that carry
  metadata.system_prompt are replayed as [system, user], the message list
  their expectations were measured against. Earlier releases sent the user
  turn alone.
• --staged-prefill replays a row's metadata.staged_prefill plan: each
  cut is sent as a token-exact /v1/completions prefix (max_tokens=1,
  vllm_xargs.semblend_stage=1), then the full prompt as token ids. TTFT
  counts from the first stage.
• --capture-hint-role marks rows of one manifest role with
  vllm_xargs.semblend_capture=1. The harness knows the roles, so this
  measures the ceiling of hinted capture, not what a router could do.
• Single-population alignment rate published beside the existing metrics
  (alignment_given_opportunity_in_class).
• Test fix: the throughput check allows for wall_seconds rounding.