bug: pubky sign-in sheet can disappear when a link cold-starts bitkit #957

Refs:

• bug: pubky sign-in from a link fails on the first try when bitkit cold-starts bitkit-android#1513
• [Bug]: Safari sign-in stalls or aborts after Bitkit approval pubky/pubky-app#2840

What happened?

On a cold start, Bitkit iOS can handle the same Pubky sign-in link twice. The second handling replaces the Authorize sheet that is already open, and the first sheet's dismiss handler then hides the replacement, so no Authorize sheet is left on screen and the sign-in stalls.

Seen in 1 of 3 cold starts while testing the Pubky App's "Authorize with Bitkit" link (pubky/pubky-app#2833) on an iPhone with only Bitkit installed. The link was handled at 11:39:03.76 and again at 11:39:04.11 CEST.

Code at eb3156a: MainNavView.swift:852, MainNavView.swift:428-456, MainNavView.swift:152, SheetViewModel.swift:52-58.

Expected behavior

A sign-in link that arrives once opens one Authorize sheet, and that sheet stays open until the user approves or declines, also on a cold start.

Steps to Reproduce

1. Force-quit Bitkit on an iPhone with only Bitkit installed.
2. On pubky.app (or the embedded Shop), choose "Authorize with Bitkit".
3. Bitkit cold-starts; sometimes the Authorize sheet appears and then disappears.
4. Tapping the link again with Bitkit running works.

Logs / Screenshots / Recordings

Screen recording available on request.

Bitkit Version

3.0.0 RC2 (current master, eb3156a)

Device / OS

iPhone, iOS 26

Reproducibility

Sometimes (1 of 3 cold starts)