Show a tooltip on each junk category explaining what it contains

[iliyami]

Users hovering over "Broken Login Items" don't know what that means. Add a .help() tooltip with a one-line explanation for each category in the results list.

Task

In FileListView.swift, attach a .help(category.description) modifier to category headers.

Add a description computed property to ScanCategory.swift:

var description: String {
    switch self {
    case .userCache: "Application cache files in ~/Library/Caches"
    case .systemCache: "System-wide cache files"
    // ... etc
    }
}

Files to change

• Sources/MacCleanKit/Models/ScanCategory.swift
• Sources/MacClean/Views/Shared/FileListView.swift