feat(sdk): add useful usdh flows

[sumfxn]

Summary

Track 4 adds the missing useful USDH flows while keeping the SDK USDH-scoped:

• swap({ from: 'USDH', to: 'USDC' }) for reverse HyperCore swaps
• getQuote() / getRoute() support for the reverse direction
• bridgeFromCore({ asset: 'USDC' | 'USDH', amount }) via Hyperliquid sendAsset
• docs + changeset for the new SDK surface

Safety

• Reverse swaps are HyperCore-only; HyperEVM direct swap remains out of scope.
• Reverse swaps reject slippageBps >= 10000 before reads/signing so the sell limit price cannot collapse to zero.
• bridgeFromCore() requires signer.address === accountAddress because the HyperEVM recipient is the Core action sender.
• bridgeFromCore() returns status: 'submitted' once Hyperliquid accepts sendAsset; it does not wait for the later HyperEVM credit.
• Bridge-out amount formatting derives EVM decimals from spotMeta instead of assuming six decimals.
• No live write-path test was run. Live validation was read-only against Hyperliquid mainnet/testnet metadata, books, quotes, and routes.
• USDC bridge-out uses the Circle-documented bare USDC token form; linked USDH uses tokenName:tokenId per Hyperliquid sendAsset docs.

References:

• Hyperliquid sendAsset docs: https://hyperliquid.gitbook.io/hyperliquid-docs/for-developers/api/exchange-endpoint#send-asset
• HyperCore <> HyperEVM transfers: https://hyperliquid.gitbook.io/hyperliquid-docs/for-developers/hyperevm/hypercore-less-than-greater-than-hyperevm-transfers
• Circle HyperCore -> HyperEVM USDC withdrawal guide: https://developers.circle.com/cctp/howtos/withdraw-usdc-from-hypercore-to-hyperevm

Validation

• pnpm lint
• pnpm build
• pnpm typecheck
• pnpm test
• git diff --check
• pnpm changeset status --since=origin/main
• live read-only probes on mainnet/testnet spotMeta, l2Book, SDK getQuote(), and SDK getRoute()