fix(canvas): 画布视觉 - 收敛边框与网格样式

web/src/lib/canvas-theme.ts

@@ -70,9 +70,9 @@ export const canvasThemes = {
     },
     dark: {
         canvas: {
-            background: "#090a0c",
-            dot: "rgba(174,184,199,.32)",
-            line: "rgba(174,184,199,.16)",
+            background: "#0b0b0b",
+            dot: "rgba(170,170,170,.22)",
+            line: "rgba(170,170,170,.10)",
             selectionFill: "rgba(255,255,255,.12)",
         },
         node: {

web/src/lib/canvas/canvas-live-viewport.ts

@@ -7,7 +7,7 @@ export const CANVAS_SELECTION_PREVIEW_EVENT = "canvas:selection-preview";
 // 空间网格点模式的点半径（像素单位）。远距（缩放 < 0.12）时用更小半径避免糊成一团。
 // 同时被 <CanvasGrid>（infinite-canvas）与滚动同步（applyCanvasLiveViewport）共享，避免两处漂移。
 export function canvasDotPx(scale: number): string {
-    return scale < 0.12 ? "1.2px" : "2px";
+    return scale < 0.12 ? "0.8px" : "1.25px";
 }
 
 export function applyCanvasLiveViewport(container: HTMLDivElement | null, viewport: ViewportTransform, notify = true) {