fix(examples/ts): align custom client env vars with .env-local

[feldmannn]

Description

The TypeScript custom client example at examples/typescript/clients/custom/index.ts reads process.env.SERVER_URL (which is not declared in this example's .env-local) and hardcodes the path /weather. As a result, developers following the .env-local template see no effect from their edits: the env-var fallback http://localhost:4021 always wins, and the path is unconfigurable despite .env-local providing ENDPOINT_PATH.

Every other client example in the same directory (fetch/, axios/) already uses the canonical three-line pattern. This PR aligns the custom client with that pattern:

const baseURL = process.env.RESOURCE_SERVER_URL || "http://localhost:4021";
const endpointPath = process.env.ENDPOINT_PATH || "/weather";
const url = `${baseURL}${endpointPath}`;

The new three-line block is byte-identical to examples/typescript/clients/fetch/index.ts:15-17 and examples/typescript/clients/axios/index.ts:16-18. No other changes to the file, the example README, or .env-local.

Disclosure: this change was prepared with the help of an AI coding assistant. The diff was independently reviewed and verified line-for-line against the canonical sibling pattern before commit.

Tests

There are no tests in examples/typescript/clients/custom/ (it ships as a runnable tsx example, not a build target). Local verification performed against main:

• pnpm install from examples/typescript/: exit 0
• pnpm-lock.yaml diff vs main: empty (passes check_package_lock.yml)
• Prettier check on the changed file (LF line endings, matching Linux CI): clean
• ESLint on the changed file (LF line endings): clean
• Byte-for-byte equality of the new 3-line block against fetch/index.ts:15-17 and axios/index.ts:16-18: confirmed

Checklist

• I have formatted and linted my code
• All new and existing tests pass
• My commits are signed (required for merge) -- you may need to rebase if you initially pushed unsigned commits
• I added a changelog fragment for user-facing changes (skipped: examples are not published as a package)

[vercel]

@feldmannn is attempting to deploy a commit to the Coinbase Team on Vercel.

A member of the Team first needs to authorize it.

[phdargen]

Thanks for the fix @feldmannn