fix: make app-server connection loss terminal

[seungpyoson]

Summary

• make app-server connection loss a single terminal transition that rejects pending RPCs, future RPCs, and turn-completion waiters
• bound initialization and owned-child teardown without adding a production turn-duration timeout
• make broker shutdown idempotent and able to close half-open clients and reap failed-startup processes
• add behavioral coverage for parse failures, non-object messages, EOF, write failures, early child exit, process-tree cleanup, and shutdown races

Motivation

The app-server client previously tracked logical protocol failure separately from process closure. Several connection-loss paths could therefore leave later requests or turn-completion waits unsettled, and initialization failure could return without reaping the owned launcher tree.

This change gives the connection one write-once terminal cause and routes every relevant protocol or process failure through it. Initialization and teardown have bounded lifecycle deadlines; normal Codex turns remain unbounded.

Testing

• npm test (106 tests)
• npm run build

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 92ed77c7f4

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".