docs: add bilingual agent collaboration workflow guide

[zxch3n]

Related issue

Internal documentation contribution; no linked issue.

Problem / pressure

Readers need a discoverable documentation guide to coordinating Claude Code, Kimi, Codex, and Grok across sessions and machines. Existing session-control docs also describe an obsolete Developer mode / Tasks beta prerequisite and omit conversation mentions.

Summary

Add an English and Chinese Agent Collaboration Workflows guide under Docs, alongside Parallel Agents and Agent Session Control near the top of the Features sidebar, covering PR/issue delegation, cross-repository fixes, review/fix loops, @ conversation mentions, and cross-machine collaboration. Include Grok in the task assignments and cross-repository example. Link the guide from Agent Session Control and update the corresponding mentions, parallel-agent, and session-control docs in both languages. Add direct guide links from the Docs homepage, Parallel Agents, and Mentions. Use descriptive bilingual titles and task-focused descriptions, reused by existing meta/OG/Twitter output. No blog post is added. Examples are illustrative prompts, not measured production results.

Before / after

Before	After
No end-to-end collaboration guide; stale setup prerequisite	Bilingual Docs guide, sidebar entry, and matching current usage documentation

Test plan

• Passed: pnpm run docs check, git diff --check, and guide documentation-link/code-fence checks.
• Verified generated sitemap contains both guide URLs; navigation placement and four incoming links per locale pass direct checks. Existing metadata output correctly produces descriptions, OG/Twitter descriptions, canonical, and language alternates for the updated content.
• Ran pnpm format; reverted its unrelated code-format changes to keep this PR documentation-only.
• Blocked: pnpm check stops at missing tsgo in this dependency-incomplete nested worktree.
• Blocked: site content generation stops at missing fumadocs-mdx; MDX build and rendered-page verification remain outstanding.

Context handoff

Instructions for reviewing agents

• Review focus: Check the bilingual documentation guide and companion docs for accurate conversation mentions, cross-machine coordination, and review/fix handoffs.
• Decisions to challenge: Ensure the illustrative prompts convey supported session workflows without implying automatic context merging or file transfer.
• Plausible failures / evidence gaps: Site MDX compilation and rendering were not verified because required dependencies are absent.

Authoring context

• User goal / directives: Prepare the accepted bilingual orchestration article and companion corrections for a PR; omit Agent Notes from this change.
• Constraints / non-goals: Documentation only; no runtime changes or website deployment.
• Risk-bearing decisions: Remove the obsolete beta prerequisite based on maintainer confirmation; preserve online-machine, access, and worktree conditions.
• Destructive or irreversible behavior: No product data changes; the unpublished local proposal note was removed as requested.
• Deliberately not done or tested: No live agent tasks, production examples, or performance measurements; no dependency installation in the nested worktree.
• Unknowns / confidence: Content and local links checked; build, rendered output, and search performance remain unverified.