feat(browser): persistent login + CDP attach mode #2809

Browser sessions now reuse a Chromium user profile across runs by default
(`~/.cow/browser_profile`), so users only log in to a site once.
Three launch modes are selectable via `tools.browser` in config.json:
  - persistent (default): Playwright Chromium with a persistent user_data_dir
  - cdp: attach to an externally launched real Chrome via `cdp_endpoint`
    (full fingerprints, ideal for sites with strict bot detection)
  - fresh: clean context every run, set `persistent: false`

Also:
  - Self-heal when the user closes the browser window mid-session: detect
    closed page/context/browser via close listeners and exception scanning,
    then transparently relaunch on the next request.
  - Graceful CDP shutdown: disconnect only, never kill the user's Chrome.
  - Friendly errors when the CDP endpoint is unreachable or the persistent
    profile is locked, so the LLM can guide the user instead of looping.
  - Fix tool config being silently overwritten by workspace config in
    AgentInitializer; per-tool user settings (e.g. browser.cdp_endpoint)
    are now merged instead of replaced.
  - Update zh / en / ja docs with the new login-persistence section,
    including the Chrome 137+ requirement to pair --remote-debugging-port
    with a dedicated --user-data-dir.

bridge/agent_initializer.py

@@ -377,12 +377,18 @@ class AgentInitializer:
                     tool = tool_manager.create_tool(tool_name)
 
                 if tool:
-                    # Apply workspace config to file operation tools
+                    # Apply workspace config to file operation tools.
+                    # Merge into the existing tool.config (set by ToolManager from
+                    # config.json's `tools.<name>` section) instead of replacing
+                    # it, otherwise per-tool user configs (e.g. browser.cdp_endpoint)
+                    # would be silently dropped.
                     if tool_name in ['read', 'write', 'edit', 'bash', 'grep', 'find', 'ls', 'web_fetch', 'send', 'browser']:
-                        tool.config = file_config
-                        tool.cwd = file_config.get("cwd", getattr(tool, 'cwd', None))
-                        if 'memory_manager' in file_config:
-                            tool.memory_manager = file_config['memory_manager']
+                        merged_config = dict(getattr(tool, 'config', None) or {})
+                        merged_config.update(file_config)
+                        tool.config = merged_config
+                        tool.cwd = merged_config.get("cwd", getattr(tool, 'cwd', None))
+                        if 'memory_manager' in merged_config:
+                            tool.memory_manager = merged_config['memory_manager']
                     tools.append(tool)
             except Exception as e:
                 logger.warning(f"[AgentInitializer] Failed to load tool {tool_name}: {e}")