fix(MessageList): prevent message pagination too early on mount

[MartinCupela]

🎯 Goal

Prevent pagination while the MessageList content is being mounted with the initial page content

It solves a threshold/race issue where:

• At viewport height 941px, message list bottom offset is 250, so no extra pagination fires; list stays at bottom.
• At viewport height 942px, bottom offset becomes 249, which is < 250, so reverse infinite-scroll treats it as “near top” and auto-loads older messages.

Root cause: A race condition between three systems during mount:

• InfiniteScroll fires loadPreviousPage() via its deferred rAF check when scrollTop=0 < threshold(250) — this is legitimate when content fits the viewport (sH=cH, no overflow before fonts fully load)
• Settle pass scrolls to bottom at 80ms once the layout stabilizes and overflow appears
• useMessageListScrollManager reads the stale cached scrollTop.current=0 ref when loadingMore becomes true, concludes the user was "at the absolute top," and sets stick-to-top mode
• When prepended messages arrive, stick-to-top → scrollTop=0 → jumps to top
• The settle pass re-runs but sees initialDistanceToBottom > scrolledUpThreshold → bails → stays at top

Fix: Two changes in useMessageListScrollManager:

1. When determining the older-pagination restoration mode, read the live DOM scrollTop via scrollContainerMeasures() instead of the stale cached ref (which may not have been updated if the scroll event from scrollToBottom() hasn't fired yet)
2. When the container has no overflow (scrollHeight ≤ offsetHeight), default to idle mode instead of stick-to-top, because the scroll position is meaningless in a non-scrollable container

[github-actions]

Size Change: +112 B (+0.02%)

Total Size: 672 kB

📦 View Changed

Filename	Size	Change
dist/cjs/index.js	267 kB	+51 B (+0.02%)
dist/es/index.mjs	265 kB	+61 B (+0.02%)

ℹ️ View Unchanged

Filename	Size
dist/cjs/audioProcessing.js	1.32 kB
dist/cjs/emojis.js	3.01 kB
dist/cjs/mp3-encoder.js	1.27 kB
dist/cjs/useNotificationApi.js	45.4 kB
dist/css/emoji-picker.css	178 B
dist/css/emoji-replacement.css	456 B
dist/css/index.css	39.3 kB
dist/es/audioProcessing.mjs	1.31 kB
dist/es/emojis.mjs	2.52 kB
dist/es/mp3-encoder.mjs	756 B
dist/es/useNotificationApi.mjs	45.2 kB

_{compressed-size-action}

[codecov]

Codecov Report

❌ Patch coverage is 90.90909% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 82.84%. Comparing base (deda536) to head (816d9a5).
⚠️ Report is 15 commits behind head on master.

Files with missing lines	Patch %	Lines
...t/hooks/MessageList/useMessageListScrollManager.ts	85.71%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3143      +/-   ##
==========================================
+ Coverage   82.79%   82.84%   +0.05%     
==========================================
  Files         419      419              
  Lines       12270    12278       +8     
  Branches     3951     3953       +2     
==========================================
+ Hits        10159    10172      +13     
+ Misses       2111     2106       -5     

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[stream-ci-bot]

🎉 This PR is included in version 14.1.0 🎉

The release is available on:

• GitHub release
• npm package (@latest dist-tag)

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