fix(test): scaling-ratio form for the wide-flat linearity guard#934
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An absolute wall-clock bound conflates machine speed with complexity class: the gcc-13-ARM ASan CI leg runs this extraction ~200x slower than clang at measured-perfectly-linear complexity (27.1/54.2/108.3/ 214.8s for 50k/100k/200k/400k siblings) and flunked a 30s bound on LINEAR code — the leg has always been the slow one (71min in the last fully green run, unchanged since). Assert the complexity class instead: extract the same comment-sibling fixture at 20k and 400k lines and bound the growth ratio at 40x. Calibrated from measurement, not models — the ASan builds carry a large linear per-line baseline that dilutes small-growth ratios (at 8x growth the known-quadratic pre-merge walk measured 22.4x and slipped under a 24x bound), while at 20x growth linear code measures ~20x on both toolchains and the quadratic walk measures 64x. Verified RED (64.4x, fails) against the pre-merge walk_defs and GREEN (19x) on the fix; the test now prints both timings unconditionally for future triage. Signed-off-by: Martin Vogel <martin.vogel.tech@gmail.com>
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The wide-flat guard's absolute 30s wall-clock bound failed on ubuntu-24.04-arm — that leg's gcc-13 ASan build runs extraction ~200x slower than clang at measured-perfectly-linear complexity (container-verified: 27.1/54.2/108.3/214.8s for 50k/100k/200k/400k siblings; the leg took 71min in the last fully-green run too — pre-existing).
Replaced with a scaling-ratio assertion (complexity class, machine-independent): same fixture at 20k and 400k lines, growth ratio bounded at 40x. Parameters calibrated from measurement — linear code measures ~20x on both toolchains, the known-quadratic pre-merge walk measures 64.4x (verified RED against it; smaller growth factors let it slip under the bound). Timings now print unconditionally for triage.