fix: add serverExternalPackages to Next.js template for bundler compatibility

[mvanhorn]

Description

Adds serverExternalPackages to the create-onchain-agent Next.js template to fix build failures with Next.js 16 (Turbopack and Webpack).

Closes #929

Problem

Next.js 16's Turbopack aggressively bundles server-side dependencies including @noble/hashes. The ESM exports get incorrectly tree-shaken during bundling, causing a runtime TypeError: Y is not a function when keccak256 is called via viem (a transitive dependency of AgentKit).

The error appears at build time during page data collection:

TypeError: Y is not a function
    at @noble/hashes/esm/sha3.js
    at viem/_esm/utils/hash/keccak256.js

This affects both Turbopack and Webpack bundlers in Next.js 16.

Solution

Adding @noble/hashes, @noble/curves, @scure/bip39, and @scure/bip32 to serverExternalPackages in next.config.js tells Next.js to skip bundling these packages and use Node.js require() instead. This avoids the ESM/CJS interop issue that breaks the crypto libraries.

The fix is applied to typescript/create-onchain-agent/templates/next/next.config.js so all new projects created with npm create onchain-agent@latest get the correct config.

Users with existing projects should add the same config:

const nextConfig = {
  serverExternalPackages: ["@noble/hashes", "@noble/curves", "@scure/bip39", "@scure/bip32"],
};

Tests

This is a configuration change in the project template. The fix was verified by reproducing the issue described in #929 and confirming the build succeeds with serverExternalPackages set.

Checklist

• I have formatted and linted my code
• All new and existing tests pass
• My commits are signed (required for merge)
• I added a changelog fragment for user-facing changes

This contribution was developed with AI assistance (Claude Code).

[cb-heimdall]

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