fix: check for @react-router/dev as proxy for RR7 framework mode

See https://netlify.slack.com/archives/C01TKAEBP3Q/p1733952147247699.

packages/build-info/src/frameworks/react-router.test.ts

@@ -7,7 +7,7 @@ import { Project } from '../project.js'
 beforeEach((ctx) => {
   ctx.fs = new NodeFS()
 })
-test('detects a React Router v7 site', async ({ fs }) => {
+test('detects a site using React Router v7 as a framework', async ({ fs }) => {
   const cwd = mockFileSystem({
     'react-router.config.ts': '',
     'vite.config.ts': '',
@@ -46,6 +46,32 @@ test('detects a React Router v7 site', async ({ fs }) => {
   expect(detected?.[0]?.dev?.port).toBe(5173)
 })
 
+test('does NOT detect a site using React Router v7 as a library', async ({ fs }) => {
+  const cwd = mockFileSystem({
+    'rollup.config.ts': '',
+    'package.json': JSON.stringify({
+      scripts: {
+        build: 'rollup build',
+        dev: 'rollup dev',
+        typecheck: 'react-router typegen && tsc',
+      },
+      dependencies: {
+        react: '^18.3.1',
+        'react-dom': '^18.3.1',
+        'react-router': '^7.0.2',
+      },
+      devDependencies: {
+        rollup: '^4.28.1',
+        typescript: '^5.6.3',
+      },
+    }),
+  })
+  const detected = await new Project(fs, cwd).detectFrameworks()
+
+  const detectedFrameworks = (detected ?? []).map((framework) => framework.id)
+  expect(detectedFrameworks).not.toContain('react-router')
+})
+
 test('does NOT detect a React Router <v7 site', async ({ fs }) => {
   const cwd = mockFileSystem({
     'vite.config.ts': '',

packages/build-info/src/frameworks/react-router.ts

@@ -5,8 +5,11 @@ import { BaseFramework, Category, DetectedFramework, Framework } from './framewo
 export class ReactRouter extends BaseFramework implements Framework {
   readonly id = 'react-router'
   name = 'React Router'
+  // React Router 7+ can be used either as a library or as a framework. We want to ignore lib mode (and possibly let
+  // other frameworks/bundlers/runners be detected). There isn't a perfect way to identify a site's mode, but at the
+  // time of writing both `@react-router/dev` and `react-router.config` should only be present in framework mode.
+  npmDependencies = ['@react-router/dev']
   configFiles = ['react-router.config.ts', 'react-router.config.js']
-  npmDependencies = ['react-router']
   category = Category.SSG
 
   dev = {