Review round 4: three blocking, one major. All accepted.
**`measured_group` was sampled after the failure.** It ran inside
`signal_failure_report`, after the `kill` and after `observe_leader`,
while the framing and the function's own doc both said before. A
concurrent group change would have made the diagnostic report
post-failure state as evidence about the attempted target. It is now
sampled in `signal` before the kill and passed into the report, so the
field describes the target that was attempted rather than the state the
failure left behind.
**The Linux corroboration did not exercise the production lookup.** Its
helper read `portable_pty::process_group_leader` — the accessor this
lane stopped using on the signal path — so `pty_foreground_group` could
have fallen back on every call with every test still green. Forcing it
to always fall back demonstrates the hole exactly: the corroboration
fails, and the injected pin PASSES, because the injected tests supply
the group themselves and structurally cannot detect a broken lookup.
The helper now calls the production lookup, and the corroboration forces
only the kill so the report is built from a real terminal read. The
residual limitation is recorded rather than left to the green: on macOS
`pty_foreground_group` has no end-to-end coverage, because the platform
cannot produce the precondition.
**The framing did not update its own acceptance contract.** Revision 5
recorded Bet 1's falsification in the revision history and in the bet,
and left the normative criterion demanding the real-shell rewrite — the
"implementation quietly diverges from the contract" shape this project
already recorded as a lesson on #191/#188. Acceptance 1 now describes
the injected pin, 1a adds the corroboration and its macOS limitation,
and 4 states the sampling order. The ledger is synchronized: revision 6,
four commits, 4,471 tests, bash armed on Linux only.
**`TargetSource`'s doc had the wrong classification.** Two of the four
variants target the leader pid, not one, and the pid-versus-group split
does not line up with PTY-versus-pipe — which is why the fallback needed
its own variant rather than reusing `LeaderPid`.
Gates: 11 gates, 4,471 tests, zero failures.
Levi Neuwirth
95897f7563