docs(blog): four design questions for agent-facing Kanban

[huangruiteng]

Summary

• Add the Chinese article 《从任务看板到长程协作：Agent-facing Kanban 的四个设计问题》, covering executable transitions, bounded planning context, Task versus Goal completion, and scoped waits/human gates.
• Add a short cross-link from the existing Chinese architecture overview and list the article in the Chinese blog index. Reuse the editorial design and keep Agent-facing together in headings.
• Cite commit-pinned public implementation and test evidence. Distinguish illustrative workflows, implementation guarantees, and production qualification; no runtime behavior changes.
• Extend the existing export smoke to validate the Chinese-only article without advertising an unavailable translation.

Validation

• Public-site npm run build: passed.
• frontstage-share-bundle-smoke: passed with Python 3.13 after correcting the local default Python 3.9 environment.
• node --check and git diff --check: passed.
• Browser checks: desktop 1440 px and mobile 390 px, no horizontal page overflow; article anchors, overview link, and blog listing inspected.
• Owner reviewed and approved the local first-screen preview before commit/push.

Scope and remaining limits

One cohesive documentation/presentation commit. No private context, local state, screenshots, or generated build output included. This article is Chinese-only; English translation is not part of this change. No merge requested.