fix(mcp): remove SSE support; keep stdio default when type is omitted

- Backend: reject "sse" in validators; accept missing type as stdio; require url only for http (mcp.rs, claude_mcp.rs)
- Frontend: McpServer.type narrowed to "stdio" | "http" (optional) (src/types.ts)
- UI: avoid undefined in list item details (McpListItem)
- Claude-only sync after delete to update ~/.claude.json (commands.rs)

Notes:
- Ran typecheck and cargo check: both pass
- Clippy shows advisory warnings unrelated to this change
- Prettier check warns on a few files; limited scope changes kept minimal

src/components/mcp/McpListItem.tsx

@@ -30,9 +30,9 @@ const McpListItem: React.FC<McpListItemProps> = ({
   const enabled = server.enabled !== false;
 
   // 构建详细信息文本
-  const details = [server.type, server.command, ...(server.args || [])].join(
-    " · ",
-  );
+  const details = ([server.type, server.command, ...(server.args || [])]
+    .filter(Boolean) as string[])
+    .join(" · ");
 
   return (
     <div className={cn(cardStyles.interactive, "!p-4")}>