V3 bar vs code gap: apr serve runs Qwen3.5 one request at a time, so S3 cannot pass #5046

What

The adopted V3 bar needs m_formed == c (S3) at c = 4/8/16 on the blessed Qwen3.5-4B. But apr serve serves the hybrid model one request at a time by design (#3571): the app state holds a single Mutex<Qwen35Session>, and the code calls the hybrid "a single-stream model". There is no batch scheduler, so no Batch m=N done lines are produced. S3 cannot pass on the blessed model until a batched hybrid serving path exists. S7 may still pass, since each request decodes alone once it holds the session.

Done when

Either (a) a batched Qwen3.5 serve path exists and S3 passes at c = 4/8/16, or (b) the bar is changed by a ruling. For (b), the owner runs a planted quorum on bar versus batched path itself (C314), and a bar change needs a non-author sign-off round.

Proposed by la-0.71.1a (inbox 08:14:16Z). Refs #4971.