docs(server): call a large mainThreadReadMb a lead, not proof

The main-thread readings cover the whole sample window, so a large
read count suggests the kernel wait was a disk read but cannot prove it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
9435e92a44Victor Vogel committed on 10/24/2026, 1:03:02 AMparent869c51b

Checks

21 successful · 5 skipped
All checks passed
1 file changedLine totals unavailable