Icon: icon-fallback-rules (Guideline). Keywords: icon fallback, phosphor, heroicons, any icon, extended set. Library: Phosphor (primary) + Heroicons (fallback). Import: Primary: import { IconName } from '@phosphor-icons/react'. Fallback: import { IconName } from '@heroicons/react/24/outline' or '@heroicons/react/24/solid'.. Usage: 当默认列表中没有合适图标时：优先继续从 Phosphor 中选择任何语义更贴切的图标（不必局限于本表列出的图标）。若 Phosphor 也无合适图标，可以改用 Heroicons，并在 UI 代码中保持风格统一（线性或填充、圆角程度、笔画粗细等）。. Best For: Icon library strategy and fallback rules. Style: Outline.