Adds a per-request content fingerprint (hash of extend input-ids + seq_len) to
fwd_hash so the SAME request forwarded from an L1-hit (known-good) and an
L2-reload (suspect) can be JOINED across the log without rid (the Rust PD
gateway strips the client rid). Gated to bs<=1 forwards (the join is only
meaningful single-request, and this skips the c=24 flood forwards so the
level-3 log stays small). The analyzer joins by ck and reports the first
DETERMINISTIC stage (topk/attn) that diverges = corruption localized.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
leavelet
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