State Colocation

Phase 1 — Diagnose the Colocation Problem

Three distinct problems, three different fixes. Misidentifying them causes the wrong refactor.

Symptom	Problem	Fix
Parent holds state, only one child reads/sets it	Over-lifted state	Push down
Two siblings need the same value	State too low	Lift up to nearest common ancestor
Prop passes through 2+ components that don't use it	Drill or wrong level	Push down OR context — see §2.3
Context/store slice used by exactly one component	Over-globalized	Push down to local state
Re-renders cascade to unrelated subtrees on every state change	State too high	Push down or split context