Gate 2 A3 fail: a second member (amelia) got the same color as the first (luc),
both #E8734A. Color was assigned by COUNT(*) % palette; a deleted spike user
shifted the count so two live members landed on the same slot. Replace with
'first palette color not already in use by another user' (fall back to count
round-robin only once the palette is exhausted) — guarantees distinct, stable
colors for up to palette length members. +1 regression test (deletion frees a
slot → next member fills it, no collision).
Lucas Berger
f700182674