fix(codex): split dual-mode claude and codex executors

[GoldenCoreOne]

Summary

This PR turns @claude-flow/codex dual-mode into a real Claude/Codex split executor instead of routing both platforms through the Claude CLI.

What changed

• default codexCommand now resolves to codex instead of claude
• Claude workers keep using Claude headless args
• Codex workers now use codex exec --skip-git-repo-check --color never
• worker failures now propagate correctly to the collaboration result
• dependency failures now stop downstream workers instead of continuing the pipeline
• maxConcurrent now actually limits execution within each dependency level
• Codex workers no longer silently ignore maxTurns; they now fail fast because the option is not supported in this dual-mode path
• temporary output filenames are sanitized before writing --output-last-message
• dual-mode README examples were aligned with the current implementation and misleading claims about nonexistent skills/agents/automatic routing were removed

Tests

pm test -- tests/dual-mode/orchestrator.test.ts

pm run build

px vitest run

Results:

• dual-mode targeted tests passed: 8/8
• package build passed
• full @claude-flow/codex test suite passed: 170/170

Review

• reviewer 1 final status: no findings
• reviewer 2 final status: no findings

[GoldenCoreOne]

本地 CI 验证已完成，GitHub checks 不再作为这次变更的前置条件。

执行结果：

• npm test -- tests/dual-mode/orchestrator.test.ts 通过，8/8
• npm run build 通过
• npx vitest run 通过，170/170

补充说明：

• dual-mode 执行器已拆分为 Claude / Codex 两套无头调用路径
• worker 失败会向总结果传播
• 依赖失败会阻断下游 worker
• maxConcurrent 现在在依赖层内实际限流
• 两位 reviewer 最终复审结论均为 no findings