DeepSeek Harness subagent delegation enhancement

Key features

• SubagentStartRequest has no cwd field, and the in-process drive layer builds child session meta purely from childSessionMeta(parent, ...) — a per-call cwd is never forwarded.
• skips the deploymentpersona registration when preset AND persona are both given
• The tool surface is a bundle.
• Everything dsh-subagent-tools verifies (per-call model/provider/persona/ toolFilter, @preset:, presetHints)
• Two code paths create in-process children, and both must be patched or you hit the classic trap where the foreground path honors cwd while the background path silently ignores it