New debugging skill that traces every button/touchpoint through its full
state change sequence. Catches bugs where functions individually work but
cancel each other out via shared state side effects.
Covers 6 bug patterns:
1. Sequential Undo — call B resets what call A just set
2. Async Race — double-click bypasses state-based loading guards
3. Stale Closure — useCallback captures old value
4. Missing State Transition — handler doesn't do what label says
5. Conditional Dead Path — condition always false, action unreachable
6. useEffect Interference — effect undoes button action
Battle-tested: found 48 bugs in a production React+Zustand app that
systematic debugging (54 bugs found separately) completely missed.
