How to diff two .asl.json files?

## System details (run `AWS: About` and/or `Amazon Q: About`)

```
Extension Version: 3.78.0

VS Code Version: 1.104.1
Commit: 0f0d87fa9e96c856c5212fc86db137ac0d783365
Date: 2025-09-17T23:36:24.973Z (2 wks ago)
Electron: 37.3.1
ElectronBuildId: 12404162
Chromium: 138.0.7204.235
Node.js: 22.18.0
V8: 13.8.258.31-electron.0

OS: Darwin arm64 23.1.0
```

## Question

When I want to compare lines of two .asl.json files, AWS Toolkit overrides the default VS Code behavior of side-by-side colored diff. With a single file, I can right-click "Open with..." and choose "Built-in text editor" and all is well.

Currently I have to disable the extension to diff the lines of two files, but this gets annoying with the reload of VS Code being required, because I have setup scripts and Remote SSH extension enabled.

Any tips for a better way are appreciated!

Reproduce the comparison of two .asl.json files in VS Code with AWS Toolkit 3.78.0 enabled, then compare it with the built-in text editor behavior. Investigate the extension's editor association or diff entry point; done means users can open a colored side-by-side diff without disabling the extension or reloading VS Code.

Written by the indexing model from the issue text.