feat(web): render docs from repo-root docs/ as MDX SoT at build time

Replace the bespoke 16-section /docs page that pulled prose from
`messages/{locale}.json` with a build-time MDX renderer that reads the
canonical markdown in repo-root `docs/`. Each markdown file becomes
one section of the docs page, scrolled-to via the existing DocsShell
sidebar. Section data structure stays in `lib/docs-sections.ts` so the
sidebar / scroll-spy keeps working with no client changes.

Why this layout:

- One source of truth: `docs/guide/*.md`, `docs/reference/*.md`,
  `docs/manifesto.md`. Edits land in one place; the website redeploys
  pick them up automatically via the existing web-deploy workflow.
- Build-time only: `MDXRemote` is rendered inside an RSC and the page
  is statically generated (`●` SSG). Cloudflare Workers serves the
  rendered HTML; no MDX compiler runs at request time.
- next-intl unchanged for everything else: only the docs prose moves
  out. `mobileHeader` and `searchPlaceholder` strings stay in
  `messages/{locale}.json`; the 18 stale section keys are removed.

Files:

- web/lib/docs-sections.ts: 9 sections matching docs/ files, typed
  `DocSection` with `{ id, title, file }`.
- web/lib/docs-source.ts: `loadDocSource(file)` reads
  `<repo-root>/docs/<file>` at build time via `node:fs/promises`.
- web/components/docs/mdx-components.tsx: shadcn-styled overrides for
  every markdown element (h1-h4, p, a, ul/ol/li, blockquote, code, pre,
  table, hr, strong) so the rendered output matches the rest of the
  site.
- web/app/[locale]/docs/page.tsx: rewritten as an async RSC that loads
  every section's source in parallel and renders one MDXRemote per
  section inside DocsShell.
- web/messages/{en,ja,ko,zh}.json: `docs` key trimmed from 20 entries
  to 2 (mobileHeader, searchPlaceholder).
- web/package.json: + next-mdx-remote, + gray-matter.

Local verification: `bun run format:check`, `bun run lint`,
`bun run type-check`, `bun run build`, `bunx opennextjs-cloudflare
build` all pass; `/[locale]/docs` builds as static for all 4 locales
at 4.12 kB / 132 kB First Load.

web/messages/zh.json

@@ -247,178 +247,7 @@
   },
   "docs": {
     "mobileHeader": "Oh My OpenAgent 文档",
-    "searchPlaceholder": "搜索文档...",
-    "sections": {
-      "overview": "概览",
-      "quickStart": "快速开始",
-      "configLocations": "配置文件位置",
-      "agents": "Agents",
-      "categories": "分类",
-      "skills": "Skills",
-      "backgroundTasks": "后台任务",
-      "hooks": "钩子",
-      "mcps": "MCPs",
-      "browserAutomation": "浏览器自动化",
-      "tmux": "Tmux 集成",
-      "gitMaster": "Git Master",
-      "commentChecker": "注释检查器",
-      "experimental": "实验性功能",
-      "lsp": "LSP 配置",
-      "envVars": "环境变量"
-    },
-    "overview": {
-      "title": "配置参考",
-      "description": "Oh My OpenAgent 高度自有主张，但可根据个人喜好调整。大多数用户无需配置——运行 {command} 即可开始。"
-    },
-    "quickStart": {
-      "title": "快速开始"
-    },
-    "configLocations": {
-      "title": "配置文件位置",
-      "projectLevel": "（项目级）",
-      "userLevel": "（用户级）",
-      "jsonc": "支持 JSONC 格式，允许注释和尾随逗号。"
-    },
-    "agentsSection": {
-      "title": "Agents",
-      "description": "为内置 Agent 配置特定行为：Sisyphus、Hephaestus、Oracle、Librarian、Explore、Multimodal Looker、Prometheus、Metis、Momus、Atlas 和 Sisyphus Junior。",
-      "overrideOptions": "覆盖选项",
-      "permissions": "权限",
-      "options": {
-        "model": "模型标识符（例如 openai/gpt-4o）",
-        "variant": "模型变体（max、high、medium、low）",
-        "category": "从分类继承配置",
-        "temperature": "采样温度（0-2）",
-        "topP": "Top-p 采样（0-1）",
-        "prompt": "完全覆盖系统提示词",
-        "promptAppend": "在系统提示词后追加文本",
-        "tools": "启用或禁用特定工具",
-        "disable": "禁用此 Agent",
-        "maxTokens": "响应的最大 token 数",
-        "thinking": "扩展思考配置",
-        "reasoningEffort": "推理强度：low、medium、high、xhigh"
-      },
-      "permissionValues": "ask / allow / deny",
-      "permissionDescriptions": {
-        "edit": "文件编辑能力",
-        "bash": "Bash 命令执行",
-        "webfetch": "网络请求能力",
-        "doomLoop": "无限循环覆盖",
-        "externalDirectory": "访问项目外部文件"
-      }
-    },
-    "categoriesSection": {
-      "title": "分类",
-      "description": "分类允许你定义 Agent 可以继承的共享配置。",
-      "availableOptions": "分类可用选项：{options}。",
-      "categories": {
-        "visualEngineering": "前端、UI/UX、设计任务",
-        "ultrabrain": "深度逻辑推理",
-        "deep": "自主解决问题与深入研究",
-        "artistry": "创意任务",
-        "quick": "简单、快速任务",
-        "unspecifiedLow": "低投入一般任务",
-        "unspecifiedHigh": "高投入一般任务",
-        "writing": "文档和写作"
-      }
-    },
-    "skillsSection": {
-      "title": "Skills",
-      "description": "内置技能包括 {playwright}、{agentBrowser} 和 {gitMaster}。你也可以定义自定义技能。"
-    },
-    "backgroundTasksSection": {
-      "title": "后台任务",
-      "priority": "优先级：",
-      "options": {
-        "defaultConcurrency": "默认最大并发任务数",
-        "staleTimeoutMs": "过时任务超时时间（毫秒）",
-        "providerConcurrency": "每个提供商的并发限制",
-        "modelConcurrency": "每个模型的并发限制"
-      }
-    },
-    "hooksSection": {
-      "title": "钩子",
-      "description": "钩子允许你在各个生命周期点扩展功能。"
-    },
-    "mcpsSection": {
-      "title": "MCPs",
-      "websearch": {
-        "title": "websearch",
-        "description": "由 Exa 驱动，提供高质量搜索结果。"
-      },
-      "context7": {
-        "title": "context7",
-        "description": "文档检索和上下文管理。"
-      },
-      "grepApp": {
-        "title": "grep_app",
-        "description": "GitHub 代码搜索集成。"
-      }
-    },
-    "browserAutomationSection": {
-      "title": "浏览器自动化",
-      "playwright": {
-        "tool": "playwright",
-        "description": "完整的浏览器自动化（默认）",
-        "useCase": "测试、复杂交互"
-      },
-      "agentBrowser": {
-        "tool": "agent-browser",
-        "description": "轻量级浏览器 Agent",
-        "useCase": "快速查询、简单抓取"
-      }
-    },
-    "tmuxSection": {
-      "title": "Tmux 集成",
-      "options": {
-        "enabled": "启用 Tmux 集成",
-        "layout": "Tmux 窗口布局",
-        "mainPaneSize": "主面板大小"
-      }
-    },
-    "gitMasterSection": {
-      "title": "Git Master",
-      "options": {
-        "commitFooter": "追加到提交消息的文本",
-        "includeCoAuthoredBy": "添加 Co-authored-by 标记"
-      }
-    },
-    "commentCheckerSection": {
-      "title": "注释检查器",
-      "description": "验证代码中的注释。在自定义提示词中使用 {placeholder} 占位符。"
-    },
-    "experimentalSection": {
-      "title": "实验性功能",
-      "options": {
-        "aggressiveTruncation": "积极截断输出",
-        "autoResume": "自动恢复中断的任务",
-        "preemptiveCompaction": "在达到限制前压缩上下文",
-        "truncateAllToolOutputs": "截断所有工具输出"
-      },
-      "dynamicPruning": {
-        "trigger": "dynamic_context_pruning",
-        "description": "配置动态剪枝规则，高效管理上下文窗口使用。"
-      }
-    },
-    "lspSection": {
-      "title": "LSP 配置",
-      "options": {
-        "command": "LSP 服务器命令",
-        "extensions": "匹配的文件扩展名",
-        "priority": "服务器优先级",
-        "env": "环境变量",
-        "initialization": "初始化选项",
-        "disabled": "禁用此 LSP"
-      }
-    },
-    "envVarsSection": {
-      "title": "环境变量",
-      "opencodeConfigDir": {
-        "name": "OPENCODE_CONFIG_DIR",
-        "description": "覆盖默认配置目录路径。"
-      }
-    },
-    "footer": "Oh My OpenAgent 文档 © {year}"
+    "searchPlaceholder": "搜索文档..."
   },
   "manifesto": {
     "badge": "宣言",