Fixes to animated lightbox

[gaearon]

Stacked on #6047, #6073, #6048, and #6081

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Known issues

• Slow in prod on low-end Android
  • I have a few ideas to try, otherwise might have to disable it on Android
• Incorrect positioning on Android device
  • Doesn’t happen on emulator.
• Flash of borders on the thumbnail after dismiss via swipe
• Extra high aspect is behaving weirdly https://bsky.app/profile/schlagteslinks.bsky.social/post/3l7y4l6yur72e
• I’ve had it lock up on iOS

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Fixes for known issues in the preceding stack. It would've been a pain to rebase and I had to be very careful not to break other things. This seems to be an equilibrium of features working but it's quite fragile. See commit by commit.

• Fixes swipe-up gesture stopping working if you spam it too fast during a pager slide on iOS.
• Fixes being unable to drag or perform gestures with finger(s) on the black bars on Android.
• Fixes unintended ability to paginate while in the middle of an opening or closing animation.
• A single tap in zoomed state now always zooms out and shows controls. It was too hard to make the close animation (if you pressed close after bringing up controls in a zoomed state) work well. Now it just pops you back before showing controls. Twitter does the same.
• Cropped images no longer flash their cropped edges on the first animation frame. Now they continuously expand. This needs device testing because it definitely affects perf a bit. Mostly relevant for multi-image layouts.
• The avatar first frame is now precisely positioned.

Test Plan

All of the above. Plus the usual. Try portraits/landscapes in different layouts (1, 2, 3, 4). Slow down if needed to verify animation.

ok.mov

okay.mov

[github-actions]

Old size	New size	Diff
8.12 MB	8.12 MB	136 B (0.00%)

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[gaearon]

#6159