fix(market): quote the royalty from basis points, not a float

ERC-2981 quotes an amount against a sale price rather than publishing a
rate, so the rate is read by asking for one whole token and dividing.
Doing that in floating point printed 250 basis points as
2.4999999999999996%. rateLabel scales by 10,000 in bigint first, so the
integer the contract stores comes back out intact.

Co-authored-by: Hanzo Dev <[email protected]>

src/app/collection/page.tsx

@@ -3,7 +3,6 @@
 import { ExternalLink } from '@luxfi/ui/icons'
 import { useSearchParams } from 'next/navigation'
 import { Suspense, useEffect, useMemo } from 'react'
-import { formatUnits } from 'viem'
 import { useReadContracts } from 'wagmi'
 import { ItemCard } from '@/components/ItemCard'
 import { Page } from '@/components/Page'
@@ -12,7 +11,7 @@ import { Stat } from '@/components/Stat'
 import { Card } from '@/components/ui/card'
 import type { ChainState } from '@/hooks/chain'
 import { useCollection, useCounters, useHolders, useTransfers, useTransferIds } from '@/hooks/queries'
-import { ERC165_ABI, ERC2981_ABI, ERC721_ABI, INTERFACE, ONE } from '@/lib/contracts'
+import { ERC165_ABI, ERC2981_ABI, ERC721_ABI, INTERFACE, ONE, rateLabel } from '@/lib/contracts'
 import { idFor } from '@/lib/logs'
 import { addressUrl, type Chain } from '@/lib/registry'
 import { shortenAddress } from '@/lib/utils'
@@ -68,7 +67,7 @@ function Declares({ chain, address }: { chain: Chain; address: string }) {
       </p>
       {rate ? (
         <p className="leading-relaxed text-muted-foreground">
-          royaltyInfo quotes {Number(formatUnits(rate[1], 18)) * 100}% of a sale to{' '}
+          royaltyInfo quotes {rateLabel(rate[1])} of a sale to{' '}
           <code className="font-mono text-xs">{rate[0]}</code>. That is what the contract would
           enforce on a marketplace that honours it; none is deployed on Lux, so nothing enforces it
           today.

src/app/genesis/page.tsx

@@ -15,6 +15,7 @@ import {
   GENESIS_ABI,
   GENESIS_TOKEN_ABI,
   ONE,
+  rateLabel,
 } from '@/lib/contracts'
 import * as links from '@/lib/links'
 import { addressUrl, type Chain } from '@/lib/registry'
@@ -72,7 +73,7 @@ function Collection({ chain, address }: { chain: Chain; address: `0x${string}` }
         />
         <Stat
           label="Royalty"
-          value={rate ? `${Number(formatUnits(rate[1], 18)) * 100}%` : null}
+          value={rate ? rateLabel(rate[1]) : null}
           note="declared through ERC-2981"
         />
         <Stat
@@ -90,8 +91,7 @@ function Collection({ chain, address }: { chain: Chain; address: `0x${string}` }
           Mini, 1M for Nano, and each token below reports its own.
         </p>
         <p className="text-muted-foreground">
-          The collection declares a {rate ? `${Number(formatUnits(rate[1], 18)) * 100}%` : ''}{' '}
-          royalty through ERC-2981, which a marketplace has to read and honour. There is no
+          The collection declares a {rate ? rateLabel(rate[1]) : ''} royalty through ERC-2981, which a marketplace has to read and honour. There is no
           marketplace contract on any Lux chain to read it, and this collection&rsquo;s own{' '}
           <code className="font-mono text-xs">market</code> address is zero.
         </p>

src/app/item/page.tsx

@@ -5,7 +5,6 @@ import { useQuery } from '@tanstack/react-query'
 import Link from 'next/link'
 import { useSearchParams } from 'next/navigation'
 import { Suspense, useMemo } from 'react'
-import { formatUnits } from 'viem'
 import { useReadContracts } from 'wagmi'
 import { GenesisMeta } from '@/components/Genesis'
 import { Page } from '@/components/Page'
@@ -13,7 +12,7 @@ import { Source } from '@/components/Source'
 import { Card } from '@/components/ui/card'
 import type { ChainState } from '@/hooks/chain'
 import { useCollection, useTransferIds, useTransfers } from '@/hooks/queries'
-import { ERC165_ABI, ERC2981_ABI, ERC721_ABI, GENESIS, INTERFACE, ONE } from '@/lib/contracts'
+import { ERC165_ABI, ERC2981_ABI, ERC721_ABI, GENESIS, INTERFACE, ONE, rateLabel } from '@/lib/contracts'
 import * as links from '@/lib/links'
 import { idFor } from '@/lib/logs'
 import { addressUrl, txUrl, type Chain } from '@/lib/registry'
@@ -203,7 +202,7 @@ function Body({ state, slug, address, id }: { state: Ready; slug: string; addres
         {rate ? (
           <div>
             <span className="text-muted-foreground">Royalty </span>
-            {Number(formatUnits(rate[1], 18)) * 100}% to{' '}
+            {rateLabel(rate[1])} to{' '}
             <span className="font-mono text-xs">{rate[0]}</span>, declared through ERC-2981.
           </div>
         ) : null}

src/lib/contracts.ts

@@ -74,6 +74,14 @@ export const INTERFACE = {
 /** The unit royaltyInfo is quoted against, so the answer reads as a rate. */
 export const ONE = 10n ** 18n
 
+/**
+ * The quote for one whole token, as a percentage. Basis points are integers on
+ * chain, so this rounds off the float that dividing by 1e18 introduces —
+ * 250 bps came back as 2.4999999999999996 before.
+ */
+export const rateLabel = (quoted: bigint) =>
+  `${Number((quoted * 10_000n) / ONE) / 100}%`
+
 /**
  * GenesisNFTs.sol keeps a record per token — `mapping(uint256 => TokenMeta)
  * public tokenMeta` — and its generated getter answers on chain today. It is