v1.7.4 auto 默认顺序改为优先 playwright、其次 agent-browser

- 按大爷要求调整: auto 优先 playwright(Python, domcontentloaded更宽容), 其次 agent-browser(Rust)
- capture_webpage + smart_capture 的 auto 选路同步调整
- 新增对称兜底: playwright 失败自动切 agent-browser 重试(原 agent-browser超时→playwright 逻辑保留)
- /api/backends 与前端选择器说明同步更新(auto label/priority)

app.py

@@ -955,7 +955,7 @@ async def smart_capture_playwright(url, cfg, wait_time, viewport):
 def smart_capture(url, cfg, wait_time, viewport, backend="auto"):
     """按需截图总入口：滚动截图 + 视觉大模型实时判断，返回拼接长图"""
     if backend == "auto":
-        backend = "agent-browser" if AGENT_BROWSER_AVAILABLE else "playwright"
+        backend = "playwright" if PLAYWRIGHT_AVAILABLE else "agent-browser"
 
     if backend == "agent-browser":
         result = smart_capture_agent_browser(url, cfg, wait_time, viewport)
@@ -1002,10 +1002,10 @@ def capture_webpage(
     """
     # 选择后端
     if backend == "auto":
-        if AGENT_BROWSER_AVAILABLE:
-            backend = "agent-browser"
-        elif PLAYWRIGHT_AVAILABLE:
+        if PLAYWRIGHT_AVAILABLE:
             backend = "playwright"
+        elif AGENT_BROWSER_AVAILABLE:
+            backend = "agent-browser"
         else:
             return {"success": False, "error": "No browser backend available. Install agent-browser or playwright."}
     
@@ -1049,9 +1049,19 @@ def capture_webpage(
             )
             loop.close()
             result["backend"] = "playwright"
-            return result
         except Exception as e:
-            return {"success": False, "error": str(e)}
+            result = {"success": False, "error": str(e)}
+        # playwright 失败（auto 默认优先它）→ 自动切 agent-browser 兜底重试
+        if (not result.get("success") and AGENT_BROWSER_AVAILABLE):
+            try:
+                fb = capture_with_agent_browser(
+                    url, action, scroll_times, scroll_delay, full_page, viewport, wait_time
+                )
+                fb["backend"] = "agent-browser"
+                result = fb
+            except Exception:
+                pass
+        return result
     
     elif backend == "chrome-cdp":
         # 连接已打开的 Chrome（需 --remote-debugging-port=<cdp_port>），归一化为单结果
@@ -1111,11 +1121,12 @@ def api_backends():
         "default": "auto",
         "available": available,
         "unavailable": unavailable,
-        "priority": available + unavailable,
+        # auto 优先 playwright，其次 agent-browser，再 chrome-cdp
+        "priority": ["playwright", "agent-browser", "chrome-cdp"],
         "labels": {
-            "auto": "自动（推荐：优先 agent-browser，打开超时自动回退 Playwright）",
-            "agent-browser": "agent-browser（Rust 版，反爬强、快，默认首选）",
-            "playwright": "Playwright（Python 版，domcontentloaded 更宽容，慢页面更稳）",
+            "auto": "自动（推荐：优先 Playwright，失败自动回退 agent-browser）",
+            "playwright": "Playwright（Python 版，domcontentloaded 更宽容，慢页面更稳，默认首选）",
+            "agent-browser": "agent-browser（Rust 版，反爬强、快，备选）",
             "chrome-cdp": "Chrome CDP（连接已打开的 Chrome，需 --remote-debugging-port 启动）"
         }
     })