Add muted state to Vue nodes (#5770)

## Summary

Added mute state support to Vue nodes with visual feedback and keyboard
shortcut functionality.

## Changes

- **What**: Implemented mute state (mode 2) for Vue nodes with opacity
styling and `Ctrl+M` hotkey support

## Review Focus

Visual consistency between bypass and mute states, and keyboard shortcut
conflict detection with existing hotkeys.

## Test Coverage

- Single node mute/unmute with `Ctrl+M` hotkey
- Multi-selection mute/unmute operations
- Visual state verification with opacity changes

## Related

- https://github.com/Comfy-Org/ComfyUI_frontend/pull/5715

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-5770-Add-muted-state-to-Vue-nodes-2796d73d36508143b3edfbcb782de7c1)
by [Unito](https://www.unito.io)

browser_tests/fixtures/VueNodeHelpers.ts

@@ -22,6 +22,13 @@ export class VueNodeHelpers {
     )
   }
 
+  /**
+   * Get locator for a Vue node by the node's title (displayed name in the header)
+   */
+  getNodeByTitle(title: string): Locator {
+    return this.page.locator(`[data-node-id]`).filter({ hasText: title })
+  }
+
   /**
    * Get total count of Vue nodes in the DOM
    */