[RFC] Investigate and clean up `LGraphNode.vue` (842 lines) in vueNodes

## Problem

While `renderer/extensions/vueNodes/` is generally well-organized (~160 files, ~28,000 lines), the core `LGraphNode.vue` component at 842 lines is a candidate for decomposition. It handles:

- Node rendering
- Widget management
- Slot layout
- Selection state
- Error display
- Image previews
- Drag/drop
- Context menus

This is the most complex single component in the renderer layer.

## Proposed Investigation

1. Analyze which concerns can be extracted into child components or composables
2. Identify props/events that could be simplified
3. Determine if the component can be split without breaking the render tree

## Migration Plan

- Audit first, then propose specific extractions
- Each extraction is a single PR
- Maintain visual regression test coverage

## Testing Strategy

- Existing vueNodes tests pass
- Visual regression tests catch rendering changes

┆Issue is synchronized with this [Notion page](https://www.notion.so/Issue-11094-RFC-Investigate-and-clean-up-LGraphNode-vue-842-lines-in-vueNodes-33e6d73d3650817a955bc94c476162cd) by [Unito](https://www.unito.io)

Start by auditing renderer/extensions/vueNodes/LGraphNode.vue and the existing vueNodes tests to map its rendering, widget, layout, state, preview, drag/drop, and menu concerns. Review the visual regression coverage, then document specific extraction candidates and a migration plan whose completed state preserves the render tree and keeps those tests passing.

Written by the indexing model from the issue text.