Verify: Google Doc multi-level bullets survive mammoth → nested <ul>

[aalemayhu]

Context

Shipped in #2311. Google Docs now export as .docx and pipe through mammoth + preprocessDocxHTML before DeckParser sees them. The bullet-outline → flashcards story depends on mammoth emitting nested <ul> for indented bullets — not a flat list.

What to verify

1. Create a Google Doc with this shape:
   • Top-level bullet (Q1)
     • Indented bullet (A1)
     • Indented bullet (A2)
   • Top-level bullet (Q2)
     • Indented bullet (A2)
2. Pick it from the Drive picker on 2anki.net/upload.
3. Confirm the resulting deck has 2 cards, fronts = top bullets, backs = indented children.

What to do if it fails

If mammoth flattens nested bullets, the fix is either (a) adjust `preprocessDocxHTML` to re-nest based on `

` depth or list-style classes, or (b) document that only single-level bullets work and update the help docs + empty-state copy.

Flagged by engineer in fix: Google Doc + Slides export via docx/pptx with Drive panel UX #2311 as the riskiest assumption of the docx switch.