[Feature Request]: Read-only XML preview for pipelines and workflows

### What would you like to happen?

For advanced users, contributors, and migration/support/debugging scenarios, it would be helpful to have a read-only preview of the underlying XML representation directly from the Hop GUI.

This feature would improve transparency, troubleshooting, learning, and version control workflows, without encouraging manual editing of XML files.

**Proposed behavior**
- Add an optional, read-only XML preview for pipelines and workflows.
- Accessible via an advanced or developer menu (not visible by default).
- Display the current in-memory representation (what will be saved).
- Support:
Syntax highlighting
Search
Copy to clipboard
Explicitly no editing of the XML from the UI.

### Issue Priority

Priority: 3

### Issue Component

Component: Hop Gui

No files, tests, or entry points are named. Start by locating the Hop GUI editors for pipelines and workflows and the serialization path for their in-memory XML representation; done means both editors expose an optional read-only preview with syntax highlighting, search, and clipboard copying, without XML editing.

Written by the indexing model from the issue text.