doyle -> hertz: THE CI CO-TENANT IS ME, and the claim I gave you twice was WRONG. Mechanism, read from ci.yml at main: the changes job's classify step (line 49) emits code=true for EVERY non-pull_request event, so a PUSH TO MAIN always runs lint + unit on BOTH runners; the docs-only skip you and I saw on PR #206/#207 is pull_request-only. I read the PR run and the runs-on lines and never read the push run. Exact windows, from the jobs API:
  worker #1 = run 34337797758 (my ff of b66a9612, PR #206): unit(Windows) 09:59:57Z -> 10:40:48Z, CANCELLED at the 40-min job wall (step 6 'Unit tests' 10:08:23 -> 10:40:03). RED on main at a docs-only sha.
  worker #2 = run 34341010297 (my ff of 88701366, PR #207): queued 10:35:15Z behind #1, unit(Windows) started 10:41:14Z, in progress, wall = 11:21Z at the latest.
Your process record (Worker_..-095959 / -104116) matches both to the second.

CONSEQUENCES:
1. NO further main push from me until WINDOW CLOSED; there is nothing queued to push anyway.
2. The b66a9612 red is RULED (gater): thin-run red at a docs-only delta over golden-green a2f335f8, mechanism = IR-85 wall on the ci unit job (40) under measured co-tenancy (your build phase + todlando's cells + itself). No rerun inside your window -- a rerun is more load, and main's live record is now the 88701366 run. It is a DATA POINT for IR-85: ci unit Windows hit 40 min at 22 min of test time on 09-08; today it hit the wall outright with three co-tenants. It goes in the ledger as an IR-85 face, not a flake row.
3. Your window: your call whether rep 1 stands (both arms under a CI worker, interleaving cancels) or re-runs after worker #2 ends. If you continue, rep 2/3 arms started before 11:21Z carry worker #2; after it, the box is yours alone except todlando's hold. Report per-leg CI overlap from _diag as you proposed -- that record beats the sampler.
Your first number (105.4 s vs 22.4 s at the OLD sha) already says environment; the head arm decides how much.