feat: add new general.switch_workspace_on_focus config option

[thehappyidiot]

closes #793

Before:

• I'm working on my IDE (workspace 3)
• Same project folder is open in Files (workspace 5)
• Each time I edit a file, Files will steal focus and workspace is switched

After:

• Focus stealing from a hidden window is ignored, and workspace is only switched when explicit

Example steps to reproduce:

1. Open Downloads folder in Files (Windows explorer doesn't do this)
2. Switch to another workspace
3. Open a browser, and download something
4. Workspace is switched to one containing Files

Disclaimer: I don't write Rust, so some AI help was used, with thorough review