fix: 全面审查修复 - 日志/死代码/工具卡片/技能描述

- sqlite.ts: 移除 console.warn，改用状态变量跟踪 FTS5 可用性
- tool-handlers.ts: download_file/append_file/edit_file 补充 sendLog 执行日志
- chat-area.ts: 工具卡片补齐 29 个工具的图标/名称/参数/结果渲染
- main.ts: 移除未使用的 stopAllMCPServers 导入
- skill-manager.ts: 修复 /** 注释语法错误，补充 browser*/spawn_task 工具描述

src/renderer/main.ts

@@ -25,7 +25,7 @@ import { initMemoryManager } from './services/memory-manager.js';
 import { restoreHeartbeat } from './components/settings-modal.js';
 import { restoreCronTasks } from './services/cron-manager.js';
 import { setToolEnabled, setRunCommandMode, refreshMCPTools } from './services/tool-registry.js';
-import { startAllMCPServers, stopAllMCPServers } from './services/mcp-client.js';
+import { startAllMCPServers } from './services/mcp-client.js';
 import { initToolConfirmModal } from './components/tool-confirm-modal.js';
 import { initWorkspacePanel } from './components/workspace-panel.js';
 import { initLogPanel, addLog } from './services/log-service.js';