chore(release): bump version to 2.1.6 (build 131)

Version: CURRENT_PROJECT_VERSION 130 -> 131 (project.yml, AGENTS.md, READMEs,
docs/llms.txt).

fix(flow): host-app identification now compiles in every build configuration
(Debug, TestFlight, Release). The arbiter probe and HostAppIdentity were
DEBUG-only, so TestFlight/App Store builds never knew the host bundle id and
could not auto-return after a startflow handoff. Debug-only logging and the
Home test card are unchanged.

Also includes the pending work in the tree:
- Home: single account/setup card surface (HomeAccountSurfacePolicy/Views)
- Wide screens: voice key row and centred mic placement, iPhone Duo layout
- Keyboard: clipboard skill ranking and AI skill layout updates
- Debug: account session handoff to the Simulator (+ import script)
- Docs: portfolio assets, privacy policy URL, site/README refresh

docs/osgkeyboardversion.html

@@ -3,15 +3,6 @@
 <head>
   <meta charset="utf-8">
   <meta name="viewport" content="width=device-width, initial-scale=1, viewport-fit=cover">
-  <!-- Google tag (gtag.js) -->
-  <script async src="https://www.googletagmanager.com/gtag/js?id=G-H4WM522F4C"></script>
-  <script>
-    window.dataLayer = window.dataLayer || [];
-    function gtag(){dataLayer.push(arguments);}
-    gtag('js', new Date());
-
-    gtag('config', 'G-H4WM522F4C');
-  </script>
   <title>OSGKeyboard — What's New / 更新说明</title>
   <meta name="robots" content="noindex">
   <meta name="color-scheme" content="light dark">
@@ -198,6 +189,33 @@
   <p class="empty" id="empty-zh">暂无与当前版本匹配的更新说明。</p>
   <p class="empty" id="empty-en">No release notes match this app version.</p>
 
+  <!-- ========== 2.1.6 ========== -->
+  <article class="version-block" data-version="2.1.6">
+    <div class="version-chip">2.1.6</div>
+
+    <div class="lang-block" data-lang="zh">
+      <section class="section">
+        <ul>
+          <li><strong>适配 iPhone Duo</strong>：展开内屏自动使用宽屏布局，合上后切回手机布局</li>
+          <li><strong>优化横屏键盘</strong>：iPad 与 iPhone Duo 的语音键盘底部改为系统风格按键行，iPhone 横放时键盘更矮</li>
+          <li><strong>优化首页顶部</strong>：最多只显示一张卡片，缺少权限、未登录或积分用完时直接给出下一步入口</li>
+          <li><strong>新增剪贴板 AI 技能</strong>：其他语言的内容可一键“优化”，当前语言的内容可“翻译 XX”译成目标语言</li>
+        </ul>
+      </section>
+    </div>
+
+    <div class="lang-block" data-lang="en">
+      <section class="section">
+        <ul>
+          <li><strong>iPhone Duo support</strong>: the unfolded inner display uses the wide layout automatically and returns to the phone layout when folded</li>
+          <li><strong>Better landscape keyboards</strong>: on iPad and iPhone Duo the voice keyboard ends with a row of system-style keys, and the keyboard is shorter on an iPhone held sideways</li>
+          <li><strong>Cleaner top of Home</strong>: at most one card is shown, with a clear next step when permissions are missing, you are signed out, or credits run out</li>
+          <li><strong>New clipboard AI skills</strong>: “Polish” for text in other languages, and “Translate to XX” for text in your current language</li>
+        </ul>
+      </section>
+    </div>
+  </article>
+
   <!-- ========== 2.1.0 ========== -->
   <!-- Cumulative notes for users upgrading from 1.8.0: 2.0.x were skipped as -->
   <!-- public releases, so all of their user-facing changes ship here. -->