refactor(deck-picker): move delete preparation to ViewModel

[david-allison]

Note

Assisted-by: GPT-6

Purpose / Description

low priority work, far future prep for Compose

How Has This Been Tested?

Tests added

Checklist

• You have a descriptive commit message with a short title (first line, max 50 chars).
• You have commented your code, particularly in hard-to-understand areas
• You have performed a self-review of your own code
• UI changes: include screenshots of all affected screens (in particular showing any new or changed strings)
• UI Changes: You have tested your change using the Google Accessibility Scanner

[criticalAY]

Thanks!

[criticalAY]

Ok nice