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>

Author: bennypowers

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-storybook/src/build/build.ts

@@ -6,8 +6,8 @@ import { buildAndWrite } from './rollup/buildAndWrite.js';
 import { createManagerHtml } from '../shared/html/createManagerHtml.js';
 import { createPreviewHtml } from '../shared/html/createPreviewHtml.js';
 import { findStories } from '../shared/stories/findStories.js';
-import { StorybookPluginConfig } from '../shared/config/StorybookPluginConfig.js';
-import { StorybookConfig } from '../shared/config/StorybookConfig.js';
+import { type StorybookPluginConfig } from '../shared/config/StorybookPluginConfig.js';
+import { type StorybookConfig } from '../shared/config/StorybookConfig.js';
 
 interface BuildPreviewParams {
   type: string;

packages/dev-server-storybook/src/build/rollup/buildAndWrite.ts

@@ -1,4 +1,4 @@
-import { rollup, RollupOptions } from 'rollup';
+import { rollup, type RollupOptions } from 'rollup';
 
 export async function buildAndWrite(options: RollupOptions) {
   const bundle = await rollup(options);

packages/dev-server-storybook/src/build/rollup/createRollupConfig.ts

@@ -1,5 +1,5 @@
 import { createRequire } from 'node:module';
-import { Plugin, RollupOptions, RollupLog } from 'rollup';
+import { type Plugin, type RollupOptions, type RollupLog } from 'rollup';
 
 import { nodeResolve as resolve } from '@rollup/plugin-node-resolve';
 import { babel } from '@rollup/plugin-babel';

packages/dev-server-storybook/src/build/rollup/injectExportsOrderPlugin.ts

@@ -1,4 +1,4 @@
-import { Plugin } from 'rollup';
+import { type Plugin } from 'rollup';
 import { injectExportsOrder } from '../../shared/stories/injectExportsOrder.js';
 
 export function injectExportsOrderPlugin(storyFilePaths: string[]): Plugin {

packages/dev-server-storybook/src/build/rollup/mdjsPlugin.ts

@@ -1,4 +1,4 @@
-import { Plugin } from 'rollup';
+import { type Plugin } from 'rollup';
 import { mdjsToCsf } from 'storybook-addon-markdown-docs';
 
 export function mdjsPlugin(type: string): Plugin {

packages/dev-server-storybook/src/build/rollup/mdxPlugin.ts

@@ -1,4 +1,4 @@
-import { Plugin } from 'rollup';
+import { type Plugin } from 'rollup';
 import { transformMdxToCsf } from '../../shared/mdx/transformMdxToCsf.js';
 
 export function mdxPlugin(): Plugin {

packages/dev-server-storybook/src/serve/storybookPlugin.ts

@@ -1,8 +1,8 @@
 // @ts-ignore
-import { DevServerCoreConfig, getRequestFilePath, Plugin } from '@web/dev-server-core';
+import { type DevServerCoreConfig, getRequestFilePath, type Plugin } from '@web/dev-server-core';
 import { mdjsToCsf } from 'storybook-addon-markdown-docs';
 
-import { StorybookPluginConfig } from '../shared/config/StorybookPluginConfig.js';
+import { type StorybookPluginConfig } from '../shared/config/StorybookPluginConfig.js';
 import { createManagerHtml } from '../shared/html/createManagerHtml.js';
 import { createPreviewHtml } from '../shared/html/createPreviewHtml.js';
 import { readStorybookConfig } from '../shared/config/readStorybookConfig.js';