fix(products): per-chain chips show real leadership only, with the denominator

[Flotapponnier]

Spotted on /products/serialized: the row for bench 008 reads #3 OF 8 for the aggregate and then #1 ON ETHEREUM · #1 ON SOLANA · #1 ON BNB CHAIN · #1 ON BASE · #1 ON ARBITRUM. Both halves are defensible on their own, and together they mislead in two different ways.

1. Non-leader chips were not per-chain measurements

rankPerChainForBench holds exactly one real per-chain fact: the leader, from bestPerChain (one Prom roundtrip per chain, done in spec.ts). For everyone else it reused the unfiltered aggregate order, shifted one slot when the leader sat below them:

const rankOnChain = leaderIdx !== -1 && idx < leaderIdx ? idx + 2 : idx + 1;

So a chip reading #3 on Solana was the provider's global rank with a chain label attached, identical across every chain of the bench. The function's own docstring called this "a soft signal", but nothing in the rendered chip said so, and it sits directly beside chips that are real.

Non-leader chips are removed. A chip now means "leads this chain"; its absence means "does not lead here", never "ranks lower here".

2. The denominator was hidden

Per-chain fields on bench 008, checked against the live staging API:

filter	Serialized	leader	providers measured
aggregate	76.98%	StellarExpert	8
ethereum	96.84%	Serialized	4
base	76.36%	Serialized	4
solana	57.79%	Serialized	2

#1 ON SOLANA was #1 of 2, rendered in the same style as a win over a crowded field, next to #3 OF 8. Chips now read #1 of 4 on Ethereum. totalRanked comes from providersPerChain; when the bench has not stashed that set the denominator is omitted rather than backfilled with the global count, which would be a different number under the same label.

Not changed

Wins accounting already counted rank === 1 entries only, so wins and chainWins are untouched. The bench page chain tabs remain the authoritative per-chain view.

237 tests pass, typecheck clean, eslint clean on the three touched files (the repo's pre-existing lint errors in stacked-share-chart.tsx and time-series-chart/ are unrelated and also fail on dev).

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