fix: preserve preset persona for team members

[lisihao]

Summary

• add configurable memberPersonaPlacement with backward-compatible system default
• allow prompt placement to keep the child preset deployment persona unchanged
• persist the full member protocol in the initial user message for prompt mode
• add regression coverage for providers without scoped persona support
• document Anchored Standard and other trajectory-sensitive preset usage

Verification

• pnpm verify
• pnpm build
• pnpm typecheck
• live DSH parent/worker Trace: identical Anchored Standard first system persona and bash + str_replace_editor bootstrap tools

[NanmiCoder]

感谢保留 preset persona 的实现和 trace。成员创建与冷恢复正在统一适配，这个 PR 应在新的成员边界上重基。请保留 system 默认，并验证 prompt 模式的首次 turn、冷恢复/fork、provider persona 能力、工具限制和模型/推理力度继承；这样能保留该功能而不覆盖兼容修复。