fix(graphql-codegen): use undici fetch and add browserCompatible option

[pyramation]

Summary

Fixes two issues in the fetch process for GraphQL schema introspection (build-time) and adds a new browserCompatible config option for generated runtime code.

Build-time fixes (fetch-schema.ts)

Problem 1: Wrong fetch implementation - The code was using Node.js's global fetch() instead of undici's fetch(), which meant the dispatcher option (used for custom DNS resolution) was being ignored.

Problem 2: Incorrect DNS lookup callback - The custom DNS lookup function wasn't handling the all: true option correctly. When opts.all is true, the callback expects an array of address objects [{address, family}], not individual parameters (err, address, family).

New feature: browserCompatible option for generated code

Added a new config option to control the fetch implementation in generated runtime code:

{
  browserCompatible?: boolean; // default: true
}

• true (default): Generated code uses native W3C fetch API (works in browsers and Node.js)
• false: Generated code uses undici fetch with dispatcher support for localhost DNS resolution (Node.js only - enables proper *.localhost subdomain resolution on macOS)

Updates since last revision

Refactored code generation to use template files instead of string-based generation:

• Created templates/ directory containing all static runtime code as real TypeScript files
• Templates: client.browser.ts, client.node.ts, orm-client.ts, select-types.ts, query-builder.ts
• Generators now read from template files at codegen time
• Templates are excluded from TypeScript compilation (they contain imports that only exist in generated output context)
• Build script copies templates to dist/ for production use

Benefits: Templates are properly typed, easier to maintain, and have IDE support.

Review & Testing Checklist for Human

• Verify templates are copied to dist: After pnpm build, check that dist/core/codegen/templates/ contains all 5 template files
• Test localhost subdomain resolution (build-time): Run cnc codegen against a GraphQL endpoint using a localhost subdomain (e.g., http://api.localhost:3000/graphql) on macOS
• Test browserCompatible: false: Generate code with browserCompatible: false and verify the generated client.ts includes undici imports and localhost agent logic
• Verify generated code compiles: When browserCompatible: false, ensure the generated code compiles and runs correctly in a Node.js environment with undici installed
• Test package installation: Install the built package in a test project and verify codegen works (templates found at runtime)

Recommended test plan:

1. Run pnpm build and verify dist/core/codegen/templates/ exists with all template files
2. Run cnc codegen against http://api.localhost:3000/graphql on macOS to test build-time fix
3. Generate code with both browserCompatible: true and browserCompatible: false, inspect the output files

Notes

• No unit tests were added for the browserCompatible option or template file reading logic
• The localhost DNS resolution logic is duplicated in build-time code and generated runtime code (when browserCompatible: false)
• When using browserCompatible: false, users must have undici installed as a runtime dependency
• 2 test snapshots were updated due to formatting differences between template files and previous string templates
• Link to Devin run: https://app.devin.ai/sessions/fcc3cfc6448d4862bb8ce07110e1f27f
• Requested by: Dan Lynch (@pyramation)

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