tip: finish process when descendants hold stdio (#50701)

[kvnloo]

Tip leaf (fork-only) — CLEAN

Maps to work-order issue #174. Upstream origin anomalyco#50701 (not touched / not promoted).

What: Finish AppProcess runs promptly when a descendant inherits stdio after the parent exits (do not wait on inherited pipes).

Commit: 0acf2f8310488eae1e91e75e71aaeba568c35f23
Origin tip SHA: ea7ffc1007ce2fd5d399d52f6e81690a0130b870

Proof: fail→pass on tip descendant-stdio tests (GREEN 3 / NEG 1 fail timing / RESTORE 3).

github_writes_origin: 0. Codex promote parked.

[github-actions]

Hey! Your PR title tip: finish process when descendants hold stdio (#50701) doesn't follow conventional commit format.

Please update it to start with one of:

• feat: or feat(scope): new feature
• fix: or fix(scope): bug fix
• docs: or docs(scope): documentation changes
• chore: or chore(scope): maintenance tasks
• refactor: or refactor(scope): code refactoring
• test: or test(scope): adding or updating tests

Where scope is the package name (e.g., app, desktop, opencode).

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[github-actions]

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