fix(amm): normalize price scales before computing price impact

[neverm1ndthat]

Fixes #1011

Summary

computePriceImpact() compared spot and effective prices at different decimal scales. An integer spot price like "1" (scale=1) and a fractional effective price like "0.91" (scale=10^12) produced wrong results because spotScaled - effectiveScaled treated them as same-scale values.

With an equal-reserve 1000/1000 pool and 100 input, the old code reported 0.00% impact instead of 9.00%.

The Fix

Bring both values to their common scale via cross-multiplication before computing percentage impact:

const commonScale = spot.scale > effective.scale ? spot.scale : effective.scale;
const spotCommon = spotScaled * (commonScale / spot.scale);
const effectiveCommon = effectiveScaled * (commonScale / effective.scale);

Testing

• All 12 existing AMM tests in test/ammCalculator.test.ts pass

[neverm1ndthat]

Hi @Kingsman-99! This PR fixes Issue #1011 - computePriceImpact() now normalizes spot and effective prices to their common decimal scale before comparing. An equal-reserve 1000/1000 pool with 100 input now correctly reports 9.00% impact instead of 0.00%. All 12 AMM tests pass. PTAL!