fix: serialize goal progress accounting

[jif-oai]

Why

Goal progress accounting can be reached from multiple completion paths for the same thread. Each path takes a progress snapshot, writes the usage delta, and then marks that snapshot as accounted. When two tool-completion hooks run at the same time, they can both observe the same unaccounted delta and charge it twice.

What changed

• Added a per-thread progress-accounting permit to GoalAccountingState.
• Held that permit across the snapshot/write/mark-accounted critical section for active-turn, idle, and tool-finish accounting.
• Added regression coverage for parallel tool-finish hooks so a shared token delta is charged once and only one progress event is emitted.

Testing

• Not run locally.
• Added parallel_tool_finish_accounts_active_goal_progress_once.

[jif-oai]

@codex review

[chatgpt-codex-connector]

💡 Codex Review

Here are some automated review suggestions for this pull request.

Reviewed commit: ca96f9287f

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".