Fix various member state with sliding sync and fix test

[7w1]

Description

Fixes some member info not being fetched when someone only appears in read receipts or replies and should fix user heros not displaying the avatars (should render cached one before updated full res one?) and should reliably fetch info on demand when a user is clicked on.

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).

[github-actions]

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Status	Preview URL	Commit	Alias	Updated (UTC)
✅ Deployment successful!	https://pr-1111-sable.raspy-dream-bb1d.workers.dev	065630e	pr-1111	Sat, 18 Jul 2026 05:41:19 GMT