fix(host): 起浮窗不再经 cmd/start（那个黑控制台窗口）；feat(shell): 相机按钮一键切换截图隐藏 + 标准齿轮设置图标

- 黑窗根因：spawnShell 用 cmd /c start 跑 .cmd，start 会新建控制台，批处理里的中文还被按 GBK 解析成乱码报错。
  改成 spawn('powershell.exe', [-WindowStyle Hidden -File ...]) detached + windowsHide，无窗启动
- 标题栏新增相机按钮：一键切换『截图时隐藏本窗』（高亮=隐藏生效），设置面板里那项同步；
  开发期要截图给别人看，点一下就可见
- 设置图标从'小太阳'换成标准齿轮

shell/ui.html

@@ -568,10 +568,16 @@
                     <path d="M4 9V5h4M20 15v4h-4M20 9V5h-4M4 15v4h4" />
                 </svg>
             </button>
+            <button class="tbtn" id="bShot" title="截图时隐藏本窗（Agent 抓屏看不到）；想看效果就关掉它">
+                <svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.8" stroke-linecap="round" stroke-linejoin="round">
+                    <path d="M4 8.5h3l1.4-2h7.2L17 8.5h3v10H4z" />
+                    <circle cx="12" cy="13.2" r="3.1" />
+                </svg>
+            </button>
             <button class="tbtn" id="bSet" title="设置">
-                <svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.8" stroke-linecap="round">
-                    <circle cx="12" cy="12" r="3" />
-                    <path d="M12 3v2M12 19v2M3 12h2M19 12h2M5.6 5.6l1.4 1.4M17 17l1.4 1.4M18.4 5.6L17 7M7 17l-1.4 1.4" />
+                <svg viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.7" stroke-linecap="round" stroke-linejoin="round">
+                    <circle cx="12" cy="12" r="3.1" />
+                    <path d="M19.4 15a1.65 1.65 0 0 0 .33 1.82l.06.06a2 2 0 1 1-2.83 2.83l-.06-.06a1.65 1.65 0 0 0-1.82-.33 1.65 1.65 0 0 0-1 1.51V21a2 2 0 1 1-4 0v-.09A1.65 1.65 0 0 0 9 19.4a1.65 1.65 0 0 0-1.82.33l-.06.06a2 2 0 1 1-2.83-2.83l.06-.06A1.65 1.65 0 0 0 4.6 15a1.65 1.65 0 0 0-1.51-1H3a2 2 0 1 1 0-4h.09A1.65 1.65 0 0 0 4.6 9a1.65 1.65 0 0 0-.33-1.82l-.06-.06a2 2 0 1 1 2.83-2.83l.06.06A1.65 1.65 0 0 0 9 4.6a1.65 1.65 0 0 0 1-1.51V3a2 2 0 1 1 4 0v.09a1.65 1.65 0 0 0 1 1.51 1.65 1.65 0 0 0 1.82-.33l.06-.06a2 2 0 1 1 2.83 2.83l-.06.06A1.65 1.65 0 0 0 19.4 9v0a1.65 1.65 0 0 0 1.51 1H21a2 2 0 1 1 0 4h-.09a1.65 1.65 0 0 0-1.51 1z" />
                 </svg>
             </button>
             <button class="tbtn" id="bClose" title="关闭">
@@ -666,6 +672,7 @@
             $('bPin').classList.toggle('on', S.posLock)
             $('bLock').classList.toggle('on', S.sizeLock)
             $('bTop').classList.toggle('on', S.topmost)
+            $('bShot').classList.toggle('on', S.exclude)
             $('sTop').classList.toggle('on', S.topmost)
             $('sPin').classList.toggle('on', S.posLock)
             $('sLock').classList.toggle('on', S.sizeLock)
@@ -836,6 +843,7 @@
         $('bFull').onclick = () => cmd('fullscreen')
         $('bClose').onclick = () => cmd('close')
         $('bSet').onclick = () => $('settings').classList.toggle('show')
+        $('bShot').onclick = () => cmd('exclude')
         $('bSess').onclick = () => { const el = $('sessList'); renderSessions(); el.classList.toggle('show') }
         $('sTop').onclick = () => cmd('topmost')
         $('sPin').onclick = () => cmd('posLock')