fix: stabilize Home tab refresh and navigation

[infinityf4p]

Repeatedly tapping Home after scrolling could hang the feed on iOS 26 when an animated return to the top overlapped refresh updates. Reselecting Home from a thread or search could also refresh unexpectedly after UIKit changed the navigation stack.

Home now handles reselection before UIKit changes navigation: the first tap closes detail/search, and a subsequent tap refreshes the feed. Returning to the top uses a separate nonanimated transaction, while the refresh indicator keeps its normal animation. Repeated taps during an active refresh still return to the top and reuse the existing request.

Validation:

• 830 unit tests passed; 6 skipped.
• 19 UI regression runs passed across iOS 16.4, iOS 26.5, and iPadOS 18.3.1, including five consecutive refresh cycles with normal animations, in-flight refresh deduplication, detail/search return, pagination, pull-to-refresh, and ordinary tab switching.
• Added the four new Home refresh UI regressions to CI.
• git diff --check passed.

Remote ci-ok passed, including the Release build. The first CI UI pass had one query timeout while swiping during the in-flight refresh test; the built-in retry passed all 13 tests. Follow-up checks on the same commit passed 10 consecutive in-flight refresh runs and the complete 13-test CI UI sequence on a newly created iOS 26.5 simulator, both without retries. The original CI timeout has no app stack trace in the available log, so its cause remains unconfirmed.