feat: add server: false mode and simplify external services config

[productdevbook]

Summary

This PR introduces two major improvements to nitro-graphql:

1. Client-Only Mode (server: false)

A new configuration option that allows using nitro-graphql purely as a client-side type generator without including any server-side GraphQL code.

Use case: When you want to consume external GraphQL APIs without running your own GraphQL server.

graphql: {
  framework: 'graphql-yoga',
  server: false,
  externalServices: [
    {
      name: 'api',
      endpoint: 'https://api.example.com/graphql',
    },
  ],
}

What gets disabled:

• GraphQL route handlers (/api/graphql, /api/graphql/health)
• Schema, resolver, and directive scanning
• Server type generation (#graphql/server)
• Server scaffold files (schema.ts, config.ts, context.ts)
• Auto-import utilities (defineResolver, etc.)

What still works:

• External services client type generation (#graphql/client/{serviceName})
• SDK generation for external services
• Document scanning and hot reload

2. Simplified External Services Configuration

Reduced the required configuration from 4+ fields to just 2 fields for the common case.

Before (verbose):

externalServices: [
  {
    name: 'api',
    endpoint: 'https://api.example.com/graphql',
    schema: 'https://api.example.com/graphql',  // same as endpoint!
    downloadSchema: true,  // usually want this
  },
]

After (simple):

externalServices: [
  {
    name: 'api',
    endpoint: 'https://api.example.com/graphql',
  },
]

Smart defaults:

• schema defaults to endpoint if not specified
• downloadSchema defaults to true for URL schemas (enables offline caching)

Advanced options still available:

{
  name: 'api',
  endpoint: 'https://api.example.com/graphql',
  schema: './local-schema.graphql',  // use local schema file
  downloadSchema: 'always',  // always check for updates
  headers: { Authorization: 'Bearer xxx' },
  documents: ['graphql/**/*.graphql'],
}

3. Bug Fixes

• Hot reload for Nitro projects: Fixed missing watchDirs entry for the client directory in Nitro (non-Nuxt) projects
• Dev reload hook: Added dev:reload hook for client-only mode to ensure file changes trigger type regeneration

Test plan

• Test server: false with external service - types and SDK generated correctly
• Test simplified external services config - schema introspection works
• Test hot reload - file changes trigger regeneration
• Test offline mode - cached schema used when endpoint unreachable

🤖 Generated with Claude Code