Keep Codex updates responsive and add update simulation

[lynnswap]

Purpose

Keep ReviewMonitor responsive while checking for Codex updates and discovering the executable for a runtime restart. Add a repeatable simulation for investigating the reported slowdown through the normal Update button and runtime lifecycle.

Changes

• Run the complete update check, including file resolution and doctor JSON decoding, outside the main actor. Resolve the executable for each new runtime process in a detached task, then check acquisition cancellation before starting the runtime factory.
• Present update timing choices asynchronously as a sheet when the main window is visible, allowing main-actor tasks to continue while awaiting a choice.
• Add REVIEW_MONITOR_SIMULATE_CODEX_UPDATE=1 to the Xcode scheme as a disabled option and document its use. The simulation performs a one-second check and a ten-second installation wait using the existing subprocess runners, then stops and restarts the live Codex runtime without changing Codex or Homebrew packages.
• Cover environment selection, simulated installation, background execution, cancellation during executable resolution, and both update timing choices in regression tests.

Testing

• swift test --build-system swiftbuild --no-parallel: all 1,256 package tests passed.
• xcodebuild test -project Tools/ReviewMonitor/CodexReviewMonitor.xcodeproj -scheme CodexReviewMonitor -destination 'platform=macOS,arch=arm64' CODE_SIGNING_ALLOWED=NO CODE_SIGNING_REQUIRED=NO -skipMacroValidation: all 48 app tests passed. Macro validation uses the same opt-out as repository CI and local builds.
• git diff --check: passed.
• codex-review against main: completed with no findings using pinned base 15bc72add2c570c65bf800cec28674dabe092765 (job F6A1BDF1-6604-47ED-9050-F6BB07F4E734).

Actual Homebrew installation and an end-to-end reproduction of the reported severe slowdown remain unverified.

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-01T23:40:33.325792Z	5a09b9f	Manual request

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" or "@codex security review".

Codex reacts with 👀 while any review is running, comments if it has suggestions, and reacts with 👍 once all reviews finish with no findings.

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: 78161e7634

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".

[lynnswap]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Chef's kiss.

Reviewed commit: 5a09b9f246

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".