[feat] Merge ComfyUI_devtools into ComfyUI_frontend (#5166)

## Summary
Merges ComfyUI devtools components into the ComfyUI frontend monorepo to
consolidate development tools.

## Changes
- Added devtools components from ComfyUI repository
- Integrated development nodes and utilities
- Consolidated fake model assets for testing

## Related Issues
Fixes #4683

## Testing
- Devtools components are now available within the frontend monorepo
- Development workflow remains consistent

Co-authored-by: Claude <noreply@anthropic.com>

tools/devtools/README.md

@@ -0,0 +1,28 @@
+# ComfyUI DevTools
+
+This directory contains development tools and test utilities for ComfyUI, previously maintained as a separate repository at `https://github.com/Comfy-Org/ComfyUI_devtools`.
+
+## Contents
+
+- `__init__.py` - Server endpoints for development tools (`/api/devtools/*`)
+- `dev_nodes.py` - Development and testing nodes for ComfyUI
+- `fake_model.safetensors` - Test fixture for model loading tests
+
+## Purpose
+
+These tools provide:
+- Test endpoints for browser automation
+- Development nodes for testing various UI features
+- Mock data for consistent testing environments
+
+## Usage
+
+During CI/CD, these files are automatically copied to the ComfyUI `custom_nodes` directory. For local development, copy these files to your ComfyUI installation:
+
+```bash
+cp -r tools/devtools/* /path/to/your/ComfyUI/custom_nodes/ComfyUI_devtools/
+```
+
+## Migration
+
+This directory was created as part of issue #4683 to merge the ComfyUI_devtools repository into the main frontend repository, eliminating the need for separate versioning and simplifying the development workflow.