UX: Drive panel shape-hint reuses dropHint CSS — verify visual weight

[aalemayhu]

Context

Shipped in #2311. The Drive-panel hint ("Docs work best as a bulleted outline — top bullet asks, indented bullet answers") reuses the `dropHint` CSS class from the local dropzone.

What to check

Open https://2anki.net/upload, click the Google Drive chip. The hint line should:

• Sit visually subordinate to the action copy ("Pick a file from your Google Drive…")
• Not compete with the "Choose from Google Drive" button
• Wrap cleanly on mobile widths (320–400px)

Fix candidates if it competes

• New `shapeHint` class with smaller font / lower contrast
• Move the hint below the action button instead of above
• Render only in the empty-deck error state, not on the panel up front (this was PM's original recommendation before the trio overruled to ship everything in one PR)

Flagged by designer in #2311 as a named tradeoff.