feat: add stablecoins USDC entrypoint

[Blessing-Circle]

Adds a new viem/stablecoins entrypoint for native Circle-issued USDC on supported EVM chains.

The entrypoint includes:

• usdcAddresses: native USDC contract addresses keyed by viem chain ID
• getUsdcAddress: typed helper for resolving a native USDC address by chain ID
• getUsdcContract: convenience helper that returns a ready-to-use ERC-20 contract instance from the client's configured chain

Only native USDC deployments are included. Bridged representations such as USDC.e are intentionally excluded.

Notes

Sonic Testnet is intentionally not included. We have Sonic Testnet USDC address, but the current sonicTestnet chain definition in viem uses chain ID 64165, while the live Sonic Testnet RPC and Chainlist report chain ID 14601. To avoid exposing a USDC address under the wrong viem chain ID, this PR only includes Sonic mainnet and Sonic Blaze Testnet for now.

Validation

• Matched included addresses against Circle's USDC contract address page.
• Live-called symbol(), decimals(), and name() for included addresses where public RPCs were available.
• Confirmed Arc Testnet USDC responds with symbol = USDC, decimals = 6, and name = USDC.
• git diff --check passes.

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[changeset-bot]

🦋 Changeset detected

Latest commit: df89153

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
viem	Minor

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commit: df89153