feat(external-match): v2 API migration with backwards-compatible v1 shims

[akirillo]

Summary

Migrates the external-match package from v0 to v2 API routes internally, following the same pattern as the Rust SDK. All existing public types and methods are preserved via conversion layers (v1 order → v2, v2 response → v1), while malleable match types adopt breaking v2 input/output terminology. Adds new getMarkets(), getMarketDepth(), and getMarketDepthsAllPairs() methods; deprecated v1 methods (getSupportedTokens, getTokenPrices, getOrderBookDepth, getOrderBookDepthAllPairs) are shimmed through v2 endpoints.

Breaking changes

• ExternalMatchClient constructor: 4 args → 3 (no separate relayerUrl)
• MalleableExternalMatchResponse: rewritten with v2 input/output terminology (setInputAmount, inputBounds, outputBounds, etc.)
• AssembleExternalMatchOptions: removed requestGasSponsorship and gasRefundAddress
• Removed deprecated factory methods newSepoliaClient and newMainnetClient
• SignedGasSponsorshipInfo.signature is now optional (v2 has no separate signature)

Test plan

• pnpm typecheck passes
• pnpm build produces valid dist/
• pnpm lint passes
• Conversion functions compared line-by-line against Rust SDK v1_conversions.rs

🤖 Generated with Claude Code

[sehyunc]

Nice work — the conversion layer is faithful to the Rust SDK and the structure is clean. Two things worth looking at:

1. allow_shared is orphaned

AssembleExternalMatchOptions.allowShared still has a public field and builder method, but AssembleExternalMatchRequestV2 never includes it. Consumers will set it with no effect. Since this PR is already breaking, might be cleanest to just remove it — or at minimum mark @deprecated.

2. invertPriceString silently propagates NaN

The Rust version returns an error on parse failure. The TS version uses parseFloat which returns NaN on bad input, so you'd get 1/NaN → NaN → "NaN" flowing through as a price string. A quick guard would help:

function invertPriceString(priceStr: string): string {
    const price = Number.parseFloat(priceStr);
    if (Number.isNaN(price) || price === 0) {
        return "0";
    }
    return (1.0 / price).toString();
}