fix(editor): edgeless can't slider with finger (#15091)

fix bug edgeless can't slider with finger 

<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Added mobile immersive edgeless mode with dynamic chrome auto-hide and
tap-gesture controls.
  * Added a mobile zoom ruler UI for edgeless.
* **Bug Fixes**
* Improved iOS rendering/zoom by applying low-zoom survival behavior,
gesture-aware refresh deferral, and effective-DPR canvas scaling.
* Fixed iOS webview zoom/bounce and process-termination reload behavior.
  * Improved placeholder styling with theme-aware colors.
* **Chores**
  * Updated local ignore rules and iOS app build/version configuration.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

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Co-authored-by: DarkSky <darksky2048@gmail.com>

blocksuite/affine/gfx/connector/src/renderer/element-renderer.ts

@@ -19,6 +19,7 @@ import {
   type LocalConnectorElementModel,
   type PointStyle,
 } from '@blocksuite/affine-model';
+import { getAffinePlaceholderFillColor } from '@blocksuite/affine-shared/theme';
 import {
   getBezierParameters,
   type PointLocation,
@@ -253,7 +254,7 @@ function renderLabel(
   ctx.setTransform(matrix);
 
   if (renderer.usePlaceholder) {
-    ctx.fillStyle = 'rgba(200, 200, 200, 0.5)';
+    ctx.fillStyle = getAffinePlaceholderFillColor(renderer.getColorScheme());
     ctx.fillRect(0, 0, w, h);
     return; // Skip actual label rendering
   }