refactor(canvas): 硬编码字号/圆角清理 → 语义 token（审计 D1/P1-3） (#131)

清理画布组件散落的硬编码字号与圆角，统一走 token 体系：

字号：
- 新增 --fs-nano(7px) 覆盖原 text-[6px]/text-[7px] 子微型标注
  （角标计数、节点预览、% 后缀）
- text-[19px] → --fs-heading-lg(18px)

圆角（就近映射，±1~2px）：
- rounded-[3px] → --r-xs | rounded-[5px] → --r-sm
- rounded-[6px] → --r-sm | rounded-[7px] → --r-md
- rounded-[18px] → --r-2xl

涉及 11 个组件文件。rounded-[1px]（minimap 视口指示框，刻意尖角）保留。
颜色项（bg-white/border-stone）经核实均带 dark: 变体，属标准 Tailwind
双主题模式非误用，不在本轮处理。

Co-authored-by: sikongyue <3155157671@qq.com>

web/src/components/canvas/canvas-asset-tray.tsx

@@ -118,7 +118,7 @@ export function CanvasAssetTray({ assetImages, canvasImages, showLibrary = true,
         {
             id: "asset-tray-toggle",
             label: open ? "收起素材空间" : `打开素材空间，共 ${(showLibrary ? assetImages.length : 0) + canvasImages.length} 项`,
-            icon: <span className="relative"><Images /><span className="absolute -right-1.5 -top-1.5 min-w-3 rounded-full px-0.5 text-center text-[6px] font-bold leading-3" style={{ background: theme.accent.primary, color: "#ffffff" }}>{(showLibrary ? assetImages.length : 0) + canvasImages.length}</span></span>,
+            icon: <span className="relative"><Images /><span className="absolute -right-1.5 -top-1.5 min-w-3 rounded-full px-0.5 text-center text-[var(--fs-nano)] font-bold leading-3" style={{ background: theme.accent.primary, color: "#ffffff" }}>{(showLibrary ? assetImages.length : 0) + canvasImages.length}</span></span>,
             active: open,
             onClick: () => setOpen((value) => !value),
         },
@@ -133,7 +133,7 @@ export function CanvasAssetTray({ assetImages, canvasImages, showLibrary = true,
                         animate={{ opacity: 1, y: 0, scale: 1, rotateX: 0 }}
                         exit={{ opacity: 0, y: 14, scale: 0.95, rotateX: 3 }}
                         transition={aceternityMotion.spring.panel}
-                        className="aceternity-floating-panel absolute bottom-[50px] left-0 flex w-[min(88vw,312px)] origin-bottom-left flex-col overflow-hidden rounded-[18px] border p-2.5 backdrop-blur-2xl"
+                        className="aceternity-floating-panel absolute bottom-[50px] left-0 flex w-[min(88vw,312px)] origin-bottom-left flex-col overflow-hidden rounded-[var(--r-2xl)] border p-2.5 backdrop-blur-2xl"
                         style={{ background: theme.spatial.elevated, borderColor: theme.toolbar.border, color: theme.node.text, height: safeTrayHeight, minHeight: Math.min(TRAY_MIN_HEIGHT, getMaxTrayHeight()), maxHeight: "calc(100vh - 6rem)", boxShadow: `0 32px 100px ${theme.spatial.shadow}` }}
                     >
                         <div className="absolute inset-x-10 top-0 h-px" style={{ background: `linear-gradient(90deg, transparent, ${theme.spatial.glowStrong}, transparent)` }} />