[Feature]: Support setting simulator appearance

[rebornix]

Feature Description

I would like the AI assistant to be able to set the simulator appearance (light or dark mode) as part of the build and launch workflow. This will allow developers to ensure their app is tested under the correct visual theme, especially for UI consistency or accessibility validation.

I’ve started working on this feature in a branch and can submit a pull request soon.

Use Cases

• Verifying app styling under dark and light appearance modes

Example Interactions

You: change the simulator to dark mode
AI: I'll change the simulator back to dark mode.

[rebornix]

The codebase is well structured and it's fairly easy to contribute #27. @cameroncooke great work!