Xcode - ExplainAction

## What this prompt does:

This is the **internal system prompt** used by **Xcode**. When you use this prompt, the AI will behave exactly like Xcode's official AI agent.

### Preview of the prompt structure:

```
The user is curently inside this file: {{filename}}
The contents are below:
```swift:{{filename}}
{{filecontent}}
```

The user has selected the following code from that file:
```swift
{{selected}}
```

The user has asked:

Explain this to me.
```

### Key capabilities this prompt enables:
- Role definition and behavioral boundaries
- Tool usage and code generation rules
- Output formatting and quality standards
- Safety guardrails and edge case handling

*Full prompt length: 260 characters*