Fix thread hang edge case

[7w1]

Description

Fixes the bug that occurs when a reply to a message that also has replies (so a message in the middle of a reply chain) has a thread started on that message causing a hang.

My shortcut introduced to improve loading speeds by bypassing the SDKs on-load thread single event spam created empty fake thread events whenever it was called. It assigned each of those as a thread root message, bypassing the SDKs various checks. As a result, when a thread was started involving those bypassed shells, uh, they didn't always get properly reloaded and had extraneous data causing infinite loops and whatnot.

Now, long story short, there's an extra method that actually checks for the thread root along with associated fixes to reduce rerenders and calculations and... well I tried a lot of random stuff, some works, some didn't, and to be totally honest I'm not 100% sure how all these changes work.

But hey it works! I think thread performance is still a little worse than the main timeline, not specifically related to this, but that's all noted and out of scope for this PR.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings

AI disclosure:

• Partially AI assisted (clarify which code was AI assisted and briefly explain what it does).
• Fully AI generated (explain what all the generated code does in moderate detail).

AI was involved in the debugging stages to locate the issue and handled the test case updates.

[github-actions]

Deploying with    Cloudflare Workers

Status	Preview URL	Commit	Alias	Updated (UTC)
✅ Deployment successful!	https://pr-778-sable.raspy-dream-bb1d.workers.dev	a37b32b	pr-778	Fri, 08 May 2026 21:47:26 GMT