fix: simplify verification and stabilize sandbox tests

[seratch]

This pull request simplifies the Bash verification runner and fixes test-environment failures observed in the macOS Codex sandbox.

Run make format, make lint, make typecheck, and make tests sequentially. Coordinating these commands in parallel required custom completion tracking and cancellation bookkeeping, which introduced failure modes in the verification wrapper itself. Sequential execution makes each Make exit status authoritative and limits cleanup to one process group at a time.

This accepts a potential increase in elapsed time to reduce maintenance and cleanup complexity. Parallelism inside Make targets, including pytest workers, is unchanged.

• Stream command output directly and remove completion polling, PID arrays, launcher discovery, heartbeat management, and temporary step logs.
• Preserve failure and cancellation status, including cancellation immediately before waiting, and clean up remaining child processes.
• Treat Linux zombie workers and disappeared processes as stopped. Publish test PID and release markers atomically.
• Use spawn for macOS AdvancedSQLiteSession multiprocessing tests while preserving their cross-process assertions.
• Isolate mocked integration runner environments so credential removal does not affect later tests. Production credential handling is unchanged.
• Keep the Windows wrapper unchanged.

[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 2026-09-08T08:24:55.376998Z	6fef2bd	New commits
🔒 Security Review	✅ Completed 2026-09-08T08:21:37.837558Z	6fef2bd	New commits

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: 16196cd232

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".