ROOT CAUSE (confirmed by instrumentation):
Every markRead during auto-scroll mutated entries[idx].status,
causing SwiftUI to re-render the row (bold→regular, dot removed).
This changed card height, causing contentSize jumps of 10-128pt
per entry — visible as jitter.
FIX: During auto-scroll, collect entry IDs in deferredReadIDs
instead of mutating entries array. When auto-scroll stops,
flushDeferredReads() applies all status changes at once and
sends a single batched API call.
Manual scroll still marks immediately (no deferral needed since
the user controls the scroll position).
Removed all debug instrumentation.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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