feat: add Linux support, pnpm build fixes, and website updates

- Add Linux x64 platform support (运行.sh, build script, docs)
- Fix pnpm-first build logic across all launcher scripts
- Update website: 3→4 platforms, Linux in 3-step guide
- Update docs: Qwen free tier, StepFun model, 省钱提示
- Fix .gitignore for build artifacts

website/index.html

@@ -324,7 +324,7 @@
             <div class="stat-label en hidden">Chinese AI models</div>
         </div>
         <div class="stat">
-            <div class="stat-num">3</div>
+            <div class="stat-num">4</div>
             <div class="stat-label zh">平台支持</div>
             <div class="stat-label en hidden">OS platforms</div>
         </div>
@@ -385,8 +385,8 @@
             <div class="tag tag-red en hidden">One-Click</div>
             <h3 class="zh">雨林木风风格启动菜单</h3>
             <h3 class="en hidden">YuLinMuFeng-Style Launcher</h3>
-            <p class="zh">16 个功能：安装、修复、备份、还原、重置。双击就能用，小白也能搞定。</p>
-            <p class="en hidden">16 functions: install, repair, backup, restore, reset. Double-click and go.</p>
+            <p class="zh">16 个功能：安装、修复、备份、还原、重置。macOS / Windows / Linux 三系统，双击就能用。</p>
+            <p class="en hidden">16 functions: install, repair, backup, restore, reset. macOS / Windows / Linux.</p>
         </div>
         <div class="feature-card">
             <div class="tag tag-green zh">中国优化</div>
@@ -438,8 +438,8 @@
         <span class="en hidden">3 Steps</span>
     </h2>
     <p class="section-sub">
-        <span class="zh">双口 U 盘（USB-A + USB-C），Mac 和 Windows 都能插</span>
-        <span class="en hidden">Dual-port USB (USB-A + USB-C), works on Mac and Windows</span>
+        <span class="zh">双口 U 盘（USB-A + USB-C），Mac / Windows / Linux 通用</span>
+        <span class="en hidden">Dual-port USB (USB-A + USB-C), works on Mac, Windows & Linux</span>
     </p>
     <div class="steps">
         <div class="step">
@@ -454,8 +454,8 @@
             <div class="step-num">2</div>
             <div>
                 <h3 class="zh">双击启动菜单</h3><h3 class="en hidden">Double-click Launcher</h3>
-                <p class="zh">Mac 双击「启动菜单.command」，Win 双击「启动菜单.bat」</p>
-                <p class="en hidden">Mac: "启动菜单.command", Win: "启动菜单.bat"</p>
+                <p class="zh">Mac 双击「启动菜单.command」，Win 双击「启动菜单.bat」，Linux 运行「运行.sh」</p>
+                <p class="en hidden">Mac: "启动菜单.command", Win: "启动菜单.bat", Linux: "运行.sh"</p>
             </div>
         </div>
         <div class="step">