Baseline reproduces production age-order starvation; a fair discipline fixes
it end-to-end through the real CK-dequeue Lua and concurrency gating.

At the concurrency-key grain the production age-order baseline starves keys
(worst contention share 0.000 on skew); SFQ/stride/DRR fix it driving the real
CK-dequeue Lua via ckIndex rescoring. Confirms the base-queue spike's ranking at
the real #2617 seam.

Blind two-model review found the ckSkew/ckBalanced baseline starvation was a
Redis lexicographic tie-break on equal enqueue timestamps, not age order.
Redesigned scenarios so the backlog key keeps a genuinely old head and other
keys arrive via poisson, so the baseline now exercises real age-order
starvation (ckSkew baseline 0.187, worst key waits 1321ms; SFQ cuts it to 16ms).
FINDINGS corrected: lead with per-key wait (contention share is volume-confounded
for low-volume keys), and add the key fidelity limit the review surfaced: the
harness serves one key per Lua call, while production batches and re-scores a
served key mid-call, so this proves the ordering fix only at maxCount=1 and a
production fix must advance per-key state inside the batched Lua. Softened
'viable' to 'worth a design spike'.