* fix(shadow_eval): copy messages before router call and raise judge output cap
* fix(shadow_eval): lead failure detail with location and pin post-failure continuation
Shadow eval only answered "should this key adopt this auto-router". Once a key
is on the router it is invisible to the feature, because the sampling gate skips
any request the shadowed router already served, so post-adoption quality
regressions go unmeasured.
Reverse mode inverts the arms: sample the traffic the router did serve and
duplicate it against a fixed baseline_model, judged by the same blind pairwise
judge. Same job table, same attempt rows, same aggregates.
real_* stays the arm the caller was served and shadow_* the duplicated one, so
in reverse real_model is the router's pick and shadow_model is the baseline. The
active-job slot becomes one per (key, direction) so both directions can run at
once, and tier attribution in reverse reads the control request's routing
decision rather than the shadow call's write-back.