feat(harness): 用戶 CC harness（acr install-harness）+ 公開 repo 只留對外

讓「用 arcrun 開發」的用戶，他的 CC 自動載入 arcrun 防護、不退回自寫 Python。

新增 user-cc-harness（SDD: .agents/specs/user-cc-harness，本機）：
- acr install-harness：冪等裝進用戶當前專案（新/舊專案皆可），acr init 末尾也順便裝
  - CLAUDE.md arcrun 區塊（標記包夾，append 不破壞既有）
  - .claude/skills/arcrun-mindset（世界觀 + 資源去哪取 acr parts/auth-recipe）
  - .claude/commands/arcrun.md（/arcrun slash command）
  - .claude/hooks/arcrun-guard.sh（python→提醒不硬擋、暴露→exit 2、每條含正路）
  - settings.json 合併 hook（不覆蓋用戶既有 hooks/設定）
- llms.txt + README「給 AI」段：第一接觸點（用戶丟連結，CC 讀了知道第一步 install-harness）
  含 CF 憑證白話照抄式引導（不對用戶講 KV/Worker/R2 術語）
- harness 素材內嵌 npm 套件（cli/harness/，files 帶上），不依賴用戶有 arcrun repo
- 實測：空目錄/冪等/既有檔合併皆通過，tsc exit 0，npm pack 含 harness 5 檔

公開 repo 清理（richblack：用戶要用不要開發 arcrun）：
- git rm --cached 移除開發痕跡 + 思考過程出公開 repo（本機保留供 richblack 開發）：
  .claude/CLAUDE.md/AGENTS.md/.agents/docs/DECISIONS/BACKLOG/landing/.github
- .gitignore 防回流；補 MIT LICENSE

MCP（P7）納入 install-harness/update 的接點已設計，實作待 MCP 對齊（BACKLOG 另一條線）。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

landing/app/components/SiteNav.tsx

@@ -1,82 +0,0 @@
-'use client';
-
-import { useEffect, useState } from 'react';
-import Link from 'next/link';
-import AppLauncher from './AppLauncher';
-
-const API_BASE = process.env.NEXT_PUBLIC_API_BASE ?? 'https://cypher.arcrun.dev';
-
-type NavUser = {
-  display_name: string;
-  email: string;
-  avatar_url?: string;
-};
-
-export default function SiteNav({ currentPath }: { currentPath?: string }) {
-  const [user, setUser] = useState<NavUser | null | undefined>(undefined);
-
-  useEffect(() => {
-    fetch(`${API_BASE}/me`, { credentials: 'include' })
-      .then(r => r.ok ? r.json() as Promise<NavUser> : null)
-      .then(u => setUser(u))
-      .catch(() => setUser(null));
-  }, []);
-
-  const logout = async () => {
-    await fetch(`${API_BASE}/auth/logout`, { method: 'POST', credentials: 'include' });
-    window.location.href = '/';
-  };
-
-  const linkCls = (path: string) =>
-    `transition-colors text-sm ${currentPath === path ? 'text-white' : 'text-[#666] hover:text-white'}`;
-
-  return (
-    <nav className="flex items-center justify-between px-6 py-4 border-b border-[#1a1a1a]">
-      <Link href="/" className="text-white font-bold text-lg tracking-tight hover:opacity-80 transition-opacity">
-        arcrun
-      </Link>
-
-      <div className="flex items-center gap-4 text-sm">
-        <Link href="/integrations" className={linkCls('/integrations')}>Integrations</Link>
-        <Link href="/api-docs" className={linkCls('/api-docs')}>API</Link>
-        <a
-          href="https://github.com/richblack/arcrun"
-          target="_blank"
-          rel="noopener noreferrer"
-          className="text-[#666] hover:text-white transition-colors"
-        >
-          GitHub
-        </a>
-
-        {user === undefined ? (
-          // Loading — placeholder to prevent layout shift
-          <div className="w-20 h-7" />
-        ) : user ? (
-          <>
-            <AppLauncher userEmail={user.email} />
-            <Link href="/dashboard" className="flex items-center gap-2 hover:opacity-80 transition-opacity">
-              {user.avatar_url && (
-                // eslint-disable-next-line @next/next/no-img-element
-                <img src={user.avatar_url} alt="" width={26} height={26} className="rounded-full" />
-              )}
-              <span className="text-[#aaa]">{user.display_name}</span>
-            </Link>
-            <button
-              onClick={logout}
-              className="text-[#555] hover:text-[#888] transition-colors cursor-pointer"
-            >
-              登出
-            </button>
-          </>
-        ) : (
-          <Link
-            href="/login"
-            className="bg-indigo-600 hover:bg-indigo-500 text-white px-4 py-1.5 rounded-md font-medium transition-colors"
-          >
-            Get API Key
-          </Link>
-        )}
-      </div>
-    </nav>
-  );
-}