fix: importing msw/experimental throws runtime error

[christoph-fricke]

The new network-source API is not usable as soon as a project tries to import from msw/experimental. It crashes with a runtime error:

SyntaxError: The requested module './define-network.mjs' does not provide an export named 'DefineNetworkOptions'

This PR fixes the problem by using a type export in src/core/experimental/index.ts to ensure DefineNetworkOptions is stripped from the JS output.

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I initially tried to prevent such problems in the future by enabling verbatimModule syntax in tsconfig.base.json and fixing multiple TS errors reported by pnpm exec tsc --noEmit -p src/tsconfig.src.json, but it caused strange problems in CI.

Besides this, there appear to be multiple TS errors in the project. Some picked in the editor, some only reported by checking with one of the various TS config files such as pnpm exec tsc --noEmit -p ./tsconfig.test.unit.json. Some source code errors I noticed:

• /src/browser/sources/fallback-http-source.ts
• /src/browser/utils/deserializeRequest.ts
• /src/browser/utils/pruneGetRequestBody.ts

It does not look like the CI finds and reports the errors. Are you aware of these existing TypeScript problems?

[coderabbitai]

📝 Walkthrough

Walkthrough

This change converts DefineNetworkOptions from a runtime export and import to type-only exports and imports across two core files, while preserving the defineNetwork function export. The modification reduces JavaScript bundle output by removing the type from runtime values.

Changes

Cohort / File(s)	Summary
Type-only Export Conversion src/core/experimental/index.ts, src/native/index.ts	Converted DefineNetworkOptions from runtime export/import to type-only syntax, eliminating it from JavaScript output while maintaining TypeScript type information.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Poem

A rabbit's optimization hop! 🐰
DefineNetworkOptions takes flight so pure,
From runtime to types, the bundle's secure,
TypeScript magic, clean and bright,
Type-only exports shining light! ✨

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Title check	✅ Passed	The title directly addresses the main issue: fixing a runtime error caused by importing from msw/experimental due to type-only symbols being exported as values.
Description check	✅ Passed	The PR description clearly explains the runtime error, the fix applied (type-only export), and provides context about related TypeScript issues.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[christoph-fricke]

This type does not exist in glossary...

[christoph-fricke]

For some reason it has to be this separate export type {....}. export {..., type ...} appears to not strip the interface from the output /lib/core/experimental/index.mjs file (unless I was looking at some cached file...).