refactor: use import type for type-only imports (#3052)

* refactor: use `import type` for type-only imports across all packages

Add explicit `type` annotations to all type-only imports and exports.
This is a pure TypeScript syntax change with no runtime effect -- the
compiled JavaScript output is identical. It prepares for Node 24's
type stripping, which requires `import type` for type-only imports
since they are erased at runtime.

93 files changed across dev-server, test-runner, rollup-plugin, and
storybook packages.

Assisted-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

* ci: disable native strip-types on Node 22+ for ts-node compat

Node 22.18+ enables type stripping by default, preempting ts-node
and causing __dirname to be undefined when detect-module reparses
test files as ESM. Disable native strip-types so ts-node handles
.ts files until mocha is replaced with node:test.

Assisted-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: bennypowers

.github/workflows/verify-node.yml

@@ -17,7 +17,7 @@ jobs:
           - '18'
           - '20'
           - '22'
-          - 'latest'
+          - '24'
 
     steps:
       - uses: actions/checkout@v4
@@ -56,6 +56,8 @@ jobs:
 
       - name: Test
         run: npm run test:node
+        env:
+          NODE_OPTIONS: ${{ (matrix.node-version != '18' && matrix.node-version != '20') && '--no-experimental-strip-types' || '' }}
 
   verify-windows:
     timeout-minutes: 30

packages/dev-server-core/src/plugins/Plugin.ts

@@ -1,9 +1,9 @@
 import { FSWatcher } from 'chokidar';
 import Koa, { Context } from 'koa';
-import { Server } from 'net';
+import { type Server } from 'net';
 
-import { DevServerCoreConfig } from '../server/DevServerCoreConfig';
-import { Logger } from '../logger/Logger';
+import type { DevServerCoreConfig } from '../server/DevServerCoreConfig';
+import type { Logger } from '../logger/Logger';
 import { WebSocketsManager } from '../web-sockets/WebSocketsManager';
 
 export type ServeResult =

packages/dev-server-core/src/server/createServer.ts

@@ -6,9 +6,9 @@ import http2Server from 'http2';
 import fs from 'fs';
 import net, { Server, Socket, ListenOptions } from 'net';
 
-import { DevServerCoreConfig } from './DevServerCoreConfig.js';
+import type { DevServerCoreConfig } from './DevServerCoreConfig.js';
 import { createMiddleware } from './createMiddleware.js';
-import { Logger } from '../logger/Logger.js';
+import type { Logger } from '../logger/Logger.js';
 import { addPlugins } from './addPlugins.js';
 
 /**

packages/dev-server-rollup/src/index.ts

@@ -1,4 +1,4 @@
-export { RollupNodeResolveOptions, nodeResolve } from '@rollup/plugin-node-resolve';
+export { type RollupNodeResolveOptions, nodeResolve } from '@rollup/plugin-node-resolve';
 export { fromRollup } from './fromRollup.js';
 export { rollupAdapter } from './rollupAdapter.js';
 export { rollupBundlePlugin } from './rollupBundlePlugin.js';

packages/dev-server/src/config/DevServerConfig.ts

@@ -1,5 +1,5 @@
-import { DevServerCoreConfig } from '@web/dev-server-core';
-import { RollupNodeResolveOptions } from '@web/dev-server-rollup';
+import { type DevServerCoreConfig } from '@web/dev-server-core';
+import { type RollupNodeResolveOptions } from '@web/dev-server-rollup';
 
 export interface DevServerConfig extends DevServerCoreConfig {
   /**

packages/dev-server/src/config/mergeConfigs.ts

@@ -1,4 +1,4 @@
-import { DevServerConfig } from './DevServerConfig.js';
+import { type DevServerConfig } from './DevServerConfig.js';
 
 const arrayKeys = ['plugins', 'middleware'];
 

packages/dev-server/src/config/parseConfig.ts

@@ -1,9 +1,9 @@
 import { getPortPromise } from 'portfinder';
 import path from 'path';
 
-import { DevServerCliArgs } from './readCliArgs.js';
+import { type DevServerCliArgs } from './readCliArgs.js';
 import { mergeConfigs } from './mergeConfigs.js';
-import { DevServerConfig } from './DevServerConfig.js';
+import { type DevServerConfig } from './DevServerConfig.js';
 import { esbuildPlugin } from '../plugins/esbuildPlugin.js';
 import { watchPlugin } from '../plugins/watchPlugin.js';
 import { nodeResolvePlugin } from '../plugins/nodeResolvePlugin.js';

packages/dev-server/src/config/readCliArgs.ts

@@ -1,7 +1,7 @@
 import commandLineArgs from 'command-line-args';
 import commandLineUsage, { OptionDefinition } from 'command-line-usage';
 import camelCase from 'camelcase';
-import { DevServerConfig } from './DevServerConfig.js';
+import { type DevServerConfig } from './DevServerConfig.js';
 
 export interface DevServerCliArgs
   extends Partial<

packages/dev-server/src/logger/DevServerLogger.ts

@@ -1,4 +1,4 @@
-import { Logger, PluginSyntaxError } from '@web/dev-server-core';
+import { type Logger, PluginSyntaxError } from '@web/dev-server-core';
 import { codeFrameColumns } from '@babel/code-frame';
 import path from 'path';
 import { red, cyan } from 'nanocolors';

packages/dev-server/src/logger/createLogger.ts

@@ -1,4 +1,4 @@
-import { Plugin } from '@web/dev-server-core';
+import { type Plugin } from '@web/dev-server-core';
 import { DevServerLogger } from './DevServerLogger.js';
 import { logStartMessage } from './logStartMessage.js';