[DanielNetzer]

Implements issue #391.

Molecule: mol-391-6d567eb4f574ec95d82712c9
Formula: forgecell-github-issue
Base: 2a771de3bf09e07b900ef3467248ce5af9b7b379
Delivery: 2d755b5f10f140ba761cfea01656f86f3e3ce8e3

Awaiting exact-commit CI and human review. Harness-reported checks are not independent CI evidence. No merge, deployment or issue closure is authorized.

[DanielNetzer]

Review notes (LOW, not blocking):

• TestLeftoverHoldingPipeIsReconciledAfterWaitDelay always pays the 1 s WaitDelay plus SIGTERM; that's fine for one test, but don't copy the pattern widely.
• The helper process ignores errors from os.WriteFile/os.Rename. If they fail, the tests fail later with a less clear readPid error.
• Successful runs that leave leftovers now take up to 5 s longer to reconcile (and 1 s more if a leftover holds stdout/stderr). That's expected, and reconcileNote records it.

Protected regression: TestLiveManagedDescendantMakesResultUncertain failed by design (Decision 1 in #391 inverts it); accepted with --accept-protected-failures. All 12 checks passed.