[Bug]: Missing onMouseUp node events

### Frontend Version

v1.18.10

### Expected Behavior

When releasing mouse button, onMouseUp event should always be emitted

### Actual Behavior

onMouseUp doesn't get emitted after onMouseDown unless there is a mouse move inbetween

https://github.com/user-attachments/assets/33c98fd0-5dc8-409e-b226-b5c3dfbd0a98

### Steps to Reproduce

The following code was used to create a minimal replication / demonstration of the issue:

```javascript
import { app } from "../../scripts/app.js";

app.registerExtension({
name: "MouseEventBug",

async beforeRegisterNodeDef(nodeType, nodeData, app) {
if (nodeType.comfyClass == "Mouse Event Bug") {

// logging array
nodeType.prototype.debugEvents = [];
nodeType.prototype.maxEvents = 10;

// draw debug text
nodeType.prototype.onDrawForeground = function(ctx) {
ctx.font = "14px Arial";
ctx.fillStyle = "#ffffff";
ctx.textAlign = "left";

for (let i = 0; i < this.debugEvents.length; i++) {
ctx.fillText(this.debugEvents[i], 10, 30 + (i * 20));
}
};

nodeType.prototype.onMouseDown = function(e, pos, canvas) {
this.logEvent("Mouse DOWN");
return true;
// original events ignored for code simplicity, bug happens in both cases
};

nodeType.prototype.onMouseMove = function(e, pos, canvas) {
this.logEvent("Mouse MOVE");
return true;
};

nodeType.prototype.onMouseUp = function(e, pos, canvas) {
this.logEvent("Mouse UP");
return true;
};

// helper method used for the logging
nodeType.prototype.logEvent = function(text) {
this.debugEvents.unshift(text);

if (this.debugEvents.length > this.maxEvents) {
this.debugEvents.pop();
}

app.graph.setDirtyCanvas(true, true);
};
}
}
});
```

### Debug Logs

```powershell
Starting ComfyUI...
Checkpoint files will always be loaded safely.
Total VRAM 24576 MB, total RAM 32419 MB
pytorch version: 2.7.0+cu128
Enabled fp16 accumulation.
Set vram state to: NORMAL_VRAM
Device: cuda:0 NVIDIA GeForce RTX 3090 : cudaMallocAsync
Using pytorch attention
Python version: 3.12.10 (tags/v3.12.10:0cc8128, Apr 8 2025, 12:21:36) [MSC v.1943 64 bit (AMD64)]
ComfyUI version: 0.3.34
ComfyUI frontend version: 1.18.10
[Prompt Server] web root: E:\comfyui_drag_test\python_embeded\Lib\site-packages\comfyui_frontend_package\static

Import times for custom nodes:
0.0 seconds: E:\comfyui_drag_test\ComfyUI\custom_nodes\websocket_image_save.py
0.0 seconds: E:\comfyui_drag_test\ComfyUI\custom_nodes\mouseeventbug

Starting server

To see the GUI go to: http://127.0.0.1:8188
```

### Browser Logs

Mouse Event Debug extension loaded
load and start tracking of workflow workflows/Unsaved Workflow (2).json
[workflowStore] open workflow workflows/Unsaved Workflow (2).json

### Setting JSON

-

### What browsers do you use to access the UI ?

Mozilla Firefox

### Other Information

The bug was reproduced in a completely new and freshly downloaded portable ComfyUI v0.3.34 with default settings, and no other custom nodes

┆Issue is synchronized with this [Notion page](https://www.notion.so/Issue-3916-Bug-Missing-onMouseUp-node-events-1f56d73d365081b3847ce3e1a50546d7) by [Unito](https://www.unito.io)