[DIAG — do not merge] withdll stdout probe

[emeryberger]

Diagnostic to figure out why the injected process's stdout isn't captured through withdll. Probe A: trivial cmd-echo grandchild (isolates handle inheritance). Probe B: larson (real case). Probe C: larson without injection (control). Will be closed unmerged.

[emeryberger]

Mystery solved. With the current (fixed) withdll, all four probes capture the grandchild's stdout — including PROBE D, which replicates the watchdog's exact Start-Process -NoNewWindow launch:

=== PROBE D: replicate the watchdog exactly ===
  exit=0 ; probeD.txt:
    withdll.exe: Starting: `cmd /c "echo PROBE_D_GRANDCHILD_VIA_STARTPROCESS"'
    PROBE_D_GRANDCHILD_VIA_STARTPROCESS          <-- captured

And this run's actual watchdog hoard.txt now contains the benchmark's own line:

--- larson ---
withdll.exe: Starting: `.\larson.exe 4'
larson: threads=4 ops=400000 time=0.089 sec (4494473 ops/sec)   <-- captured

So the withdll fix (alloc8#14) was correct and sufficient by itself. My earlier "the fix alone didn't work" was a stale-binary observation: that CI run had fetched pre-merge alloc8 (a ~2s merge/rerun race, flagged at the time) and ran the old Detours-sample withdll. BENCH_OUT (#119) remains as belt-and-suspenders — it's more robust and is what the QoS gate parses.

Closing; diagnostic reverted.