docs: update Agent Surfaces doc - #2608

Code Review Summary

This incremental update addresses the earlier localization gap by updating all ten localized Agent Surfaces pages and the baseline, while retaining the intended English restructuring and docs-nav reorder. The section order and anchors remain coherent, and the localized pages now include the new inline UI guidance. However, the latest translation commit introduces a high-severity MDX parsing problem in the Traditional Chinese page, and two documentation accuracy issues remain from the previous review. The Traditional Chinese code examples also contain typographic quote characters that readers cannot copy as valid TypeScript. Risk level: Low (documentation/navigation change), although the zh-TW rendering defect is blocking for that locale.

Key findings

• 🔴 HIGH — zh-TW uses typographic quotes in JSX/HTML component attributes, making the localized MDX invalid.
• 🟡 MEDIUM — zh-TW code samples use typographic quotes as TypeScript delimiters.
• 🟡 MEDIUM — Full application documentation still claims “No polling,” despite SSE with polling fallback.
• 🟡 MEDIUM — Manage Agent is documented as personal-only even though Connections renders both personal and organization MCP servers.

The prior missing-localization issue is resolved in this commit. The docs server is running and ready for browser verification.

🧪 Browser testing: Will run after this review (PR touches UI code)