feat: 浏览器一期：坐标点击 + live 截图

- browser_click_at(x, y)：视口坐标点击（1280x800、左上角
  原点），越界与非数字拒绝；live 视图里用户在截图上的
  点击落点就走这个工具。
- browser_live_shot：固定文件 browser-live.png + 状态
  sidecar browser-live.json（URL/标题/时间戳），watcher
  轮询一个稳定路径即可；技能要求每次动作后都调一次，
  保持画面最新。
- MCP 新增 browser_click_at / browser_live_shot 两个工具；
  技能补 live 视图一节；测试 9 项（含 fake mouse、越界、
  live 文件与状态读回）。

cloud/tests/test_playwright.py

@@ -26,11 +26,20 @@ class _FakeLocator:
         return self._text
 
 
+class _FakeMouse:
+    def __init__(self, page):
+        self._page = page
+
+    def click(self, x, y):
+        self._page.calls.append(("mouse_click", x, y))
+
+
 class _FakePage:
     def __init__(self):
         self.url = "https://example.com/"
         self.calls = []
         self.shot_path = None
+        self.mouse = _FakeMouse(self)
 
     def title(self):
         return "Example Domain"
@@ -146,11 +155,43 @@ class BrowserTest(unittest.TestCase):
         self.assertTrue(self.browser.close()["closed"])
         self.assertTrue(self.browser.close()["closed"])
 
+    def test_click_at_and_bounds(self):
+        self.browser.navigate("https://example.com")
+        out = self.browser.click_at(100, 200)
+        self.assertTrue(out["ok"])
+        self.assertEqual(out["x"], 100)
+        self.assertIn(("mouse_click", 100, 200), self.page.calls)
+        with self.assertRaises(BrowserError):
+            self.browser.click_at(2000, 10)
+        with self.assertRaises(BrowserError):
+            self.browser.click_at("left", 10)
+
+    def test_live_shot_writes_fixed_file_and_status(self):
+        self.browser.navigate("https://example.com")
+        out = self.browser.live_shot()
+        self.assertEqual(out["image"], "browser-live.png")
+        self.assertTrue(out["bytes"] > 0)
+        self.assertTrue(os.path.exists(out["path"]))
+        with open(os.path.join(self._tmp.name,
+                               "browser-live.json")) as fh:
+            status = json.load(fh)
+        self.assertEqual(status["image"], "browser-live.png")
+        self.assertEqual(status["url"], "https://example.com")
+
 
 class FakeMCPBrowser:
     def navigate(self, url):
         return {"url": url, "title": "T", "ok": True}
 
+    def click_at(self, x, y):
+        return {"url": "https://x/", "title": "T", "ok": True,
+                "x": x, "y": y}
+
+    def live_shot(self, name=None):
+        return {"image": name or "browser-live.png",
+                "path": "/w/browser-live.png", "bytes": 456,
+                "url": "https://x/", "title": "T", "timestamp": 1}
+
     def snapshot(self):
         return {"url": "https://x/", "title": "T", "text": "hi",
                 "truncated": False}
@@ -168,7 +209,8 @@ class MCPTest(unittest.TestCase):
         for name in ("browser_navigate", "browser_snapshot",
                      "browser_click", "browser_fill",
                      "browser_evaluate", "browser_screenshot",
-                     "browser_close"):
+                     "browser_close", "browser_click_at",
+                     "browser_live_shot"):
             self.assertIn(name, names)
 
     def test_tools_call_dispatches(self):