Jarring message animation when opening keyboard

[gavinmorrow]

• [x] I have searched open and closed issues for duplicates
  • I saw #5468 and #5129 which seemed related but different.
• [x] I am submitting a bug report for existing functionality that does not work as intended
• [x] This isn't a feature request or a discussion topic

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Bug description

When opening/closing the keyboard in a chat, the animation for off-screen messages is different from the animation of on-screen messages and it is very jarring.

Steps to reproduce

• open a chat with more than a screen of messages
• open the keyboard (the animation is buggy)
• close the keyboard (the animation is buggy)

Actual result: Describe here what happens after you run the steps above (i.e. the buggy behaviour)

• When opening keyboard:
  • The messages that are about to be off-screen just disappear.
  • The on-screen messages (correctly) slide up.
  • This isn't very noticeable, but is probably the same bug.
• When closing keyboard:
  • The messages that were off-screen fade in.
  • The on-screen messages (correctly) slide down.
  • This is very jarring, as there is a period of time when messages overlap.

Expected result: Describe here what should happen after you run the steps above (i.e. what would be the correct behaviour) Both on- and off- screen messages should slide up/down to animate.

Screenshots

Video:

https://github.com/user-attachments/assets/00802c91-9da1-4c9c-bcc9-6694fea63459

Showing keyboard:

Hiding keyboard:

Device info

Device: iPhone 13

iOS version: 18.2.1

Signal version: 7.43 (573)

Link to debug log

https://debuglogs.org/ios/7.43.0/18ba9129abd0b6f49c5de985d7d8bc3435068985b4bcb2cf69edc91c3851ed9b.zip