feat: add DeepSeek Harness support

[cneicy]

Summary

• add a DeepSeek Harness Host bundle that reuses the existing cross-platform player and config
• map root-agent approval/question calls to Notification and settled root turns to Stop
• keep subagent creation, attention requests, and terminal events silent
• suppress the short completed/blocked boundary before an armed automatic Goal queues its next round
• run playback through DSH's managed subprocess service with Fiber-owned cleanup
• document DSH installation and shared configuration in English and Chinese
• add runtime-ownership, event-mapping, lifecycle, goal-continuation, and package smoke tests

Validation

• npm test (52 tests)
• npm pack --dry-run
• source directory injected into DSH with an active Host Fiber
• packed tarball extracted and injected into DSH successfully
• real root-session ask_user_question event produced an audible notification on Windows
• a live subagent completed without a parent-session notification regression
• hot reload stayed active; uninject removed the Fiber, registry row, and junction

Notes

• DSH runtime roots are determined through ctx.agents.roots(), not durable session lineage, so resumed historical subagents can notify when they are current top-level agents.
• Currently owned children are silent for their whole lifecycle. User-cancelled and restored interrupted turns stay silent.
• DSH currently exposes no generic Host event for "question UI is now visible". Question dings therefore occur when a well-formed ask_user_question tool call is committed; a later provider or cancellation failure can still leave a ding without a visible question.
• The upstream Actions run requires maintainer approval for this first-time external contribution: https://github.com/YunHerry/agent-ding/actions/runs/32568460235