Reject deep imports in GitHub Flow (#58574)

Summary:
Pull Request resolved: #58574

Redirect React Native implementation-path imports to an unresolved module in the GitHub Flow configuration so new deep imports fail type checking while supported package entry points remain available.

Changelog: [Internal]

Differential Revision: D120543258

Author: rubennorte

.flowconfig

@@ -55,6 +55,10 @@ munge_underscores=true
 module.name_mapper='^react-native$' -> '<PROJECT_ROOT>/packages/react-native/index.js'
 module.name_mapper='^react-native/react-private-interface$' -> '<PROJECT_ROOT>/packages/react-native/src/react-private-interface.js'
 module.name_mapper='^react-native/setup-env$' -> '<PROJECT_ROOT>/packages/react-native/src/setup-env.js'
+# Deep imports under React Native's implementation directories are redirected
+# to a module that does not exist. Package roots, secondary entry points, and
+# `src/fb_internal/*` stay importable.
+module.name_mapper='^react-native/\(Libraries\|src/private\|src/types\)/.*$' -> 'react-native-deep-import-is-not-part-of-the-public-api'
 module.name_mapper='^react-native/\(.*\)$' -> '<PROJECT_ROOT>/packages/react-native/\1'
 module.name_mapper='^@react-native/dev-middleware$' -> '<PROJECT_ROOT>/packages/dev-middleware'
 module.name_mapper='^@?[./a-zA-Z0-9$_-]+\.\(bmp\|gif\|jpg\|jpeg\|png\|psd\|svg\|webp\|m4v\|mov\|mp4\|mpeg\|mpg\|webm\|aac\|aiff\|caf\|m4a\|mp3\|wav\|html\|pdf\|xml\|ktx\|heic\|heif\)$' -> '<PROJECT_ROOT>/packages/react-native/Libraries/Image/RelativeImageStub'