fix(cli): correct node:cluster import for multiprocess mode

[y-tajiri]

Problem

Starting the CLI in multiprocess mode (--multiprocess / -m) crashes immediately with:

Cannot read properties of undefined (reading 'isPrimary')

packages/cli/src/util/createServer.ts imports node:cluster as a default import:

import cluster from 'node:cluster';

The project compiles to CommonJS without esModuleInterop, so this emits a .default property access. node:cluster exposes its API on the module object itself, so .default is undefined at runtime and every subsequent cluster.* access throws.

Fix

Use an import-equals require so the runtime object is the module itself, and reconcile it with @types/node (which models the API as a default export):

import clusterModule = require('node:cluster');
const cluster = (clusterModule as typeof clusterModule & { default?: typeof clusterModule }).default ?? clusterModule;

This keeps type-checking happy under the current tsconfig while working correctly at runtime.

Notes

• This commit is cherry-picked from feat: OpenTelemetry support to export metrics and tracing to an Otel collector #2807 (authorship preserved — thanks @Ignacio-Vidal). That PR bundles this bugfix together with the OpenTelemetry feature work; this PR extracts only the standalone node:cluster fix so it can be reviewed and merged independently.
• Single file changed, +5/-1. No behavior change outside multiprocess startup.

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