Fix React 19 webpack server bundle resolution and update docs

This commit addresses two issues identified in CI:

1. **Markdown link check failure**: Updated the ShakaCode contact link in
   react-19-quick-reference.md from https://www.shakacode.com/contact to
   mailto:justin@shakacode.com to fix the 404 error.

2. **Webpack server bundle build errors**: Fixed React 19 compatibility issue
   where the server bundle was incorrectly resolving React to the react-server
   condition, causing missing exports for createContext, useContext, and Component.

**Changes:**
- Update contact link in docs/upgrading/react-19-quick-reference.md
- Add explicit conditionNames configuration to all serverWebpackConfig.js files
  to prevent resolving to react-server build (only RSC bundles should use that)
- Disable react/react-in-jsx-scope ESLint rule since React 17+ uses new JSX transform

**Technical Details:**
React 19 introduced conditional package exports with a react-server condition.
When webpack targets 'node' for SSR bundles, it may include react-server in
its default conditionNames, causing client components with hooks to fail. The
fix explicitly sets conditionNames to ['node', 'require', 'import', '...']
to use the standard React build.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: justin808

docs/upgrading/react-19-quick-reference.md

@@ -169,4 +169,4 @@ bin/rails assets:precompile
 - [Full React 19 Upgrade Guide](./react-19-upgrade-guide.md)
 - [React on Rails Issues](https://github.com/shakacode/react_on_rails/issues)
 - [ShakaCode Forum](https://forum.shakacode.com)
-- [Commercial Support](https://www.shakacode.com/contact)
+- [Commercial Support](mailto:justin@shakacode.com)

eslint.config.ts

@@ -97,6 +97,9 @@ const config = tsEslint.config([
       // Custom React on Rails rules
       'react-on-rails/no-use-client-in-server-files': 'error',
 
+      // React 17+ with new JSX transform doesn't require React in scope
+      'react/react-in-jsx-scope': 'off',
+
       'no-shadow': 'off',
       'no-console': 'off',
       'function-paren-newline': 'off',

lib/generators/react_on_rails/templates/base/base/config/webpack/serverWebpackConfig.js.tt

@@ -114,6 +114,14 @@ const configureServer = () => {
   // If using the React on Rails Pro node server renderer, uncomment the next line
   // serverWebpackConfig.target = 'node'
 
+  // React 19 Fix: Explicitly set conditionNames to prevent resolving to react-server build
+  // The server bundle should use the regular React build, not the react-server build
+  // Only the RSC bundle should use react-server condition
+  if (!serverWebpackConfig.resolve) {
+    serverWebpackConfig.resolve = {};
+  }
+  serverWebpackConfig.resolve.conditionNames = ['node', 'require', 'import', '...'];
+
   return serverWebpackConfig;
 };
 

react_on_rails_pro/spec/dummy/config/webpack/serverWebpackConfig.js

@@ -123,6 +123,14 @@ const configureServer = (rscBundle = false) => {
 
   serverWebpackConfig.node = false;
 
+  // React 19 Fix: Explicitly set conditionNames to prevent resolving to react-server build
+  // The server bundle should use the regular React build, not the react-server build
+  // Only the RSC bundle should use react-server condition
+  if (!serverWebpackConfig.resolve) {
+    serverWebpackConfig.resolve = {};
+  }
+  serverWebpackConfig.resolve.conditionNames = ['node', 'require', 'import', '...'];
+
   return serverWebpackConfig;
 };
 

react_on_rails_pro/spec/execjs-compatible-dummy/config/webpack/serverWebpackConfig.js

@@ -112,6 +112,14 @@ const configureServer = () => {
   // If using the React on Rails Pro node server renderer, uncomment the next line
   // serverWebpackConfig.target = 'node'
 
+  // React 19 Fix: Explicitly set conditionNames to prevent resolving to react-server build
+  // The server bundle should use the regular React build, not the react-server build
+  // Only the RSC bundle should use react-server condition
+  if (!serverWebpackConfig.resolve) {
+    serverWebpackConfig.resolve = {};
+  }
+  serverWebpackConfig.resolve.conditionNames = ['node', 'require', 'import', '...'];
+
   return serverWebpackConfig;
 };
 

spec/dummy/config/webpack/serverWebpackConfig.js

@@ -110,6 +110,14 @@ const configureServer = () => {
   // If using the React on Rails Pro node server renderer, uncomment the next line
   // serverWebpackConfig.target = 'node'
 
+  // React 19 Fix: Explicitly set conditionNames to prevent resolving to react-server build
+  // The server bundle should use the regular React build, not the react-server build
+  // Only the RSC bundle should use react-server condition
+  if (!serverWebpackConfig.resolve) {
+    serverWebpackConfig.resolve = {};
+  }
+  serverWebpackConfig.resolve.conditionNames = ['node', 'require', 'import', '...'];
+
   return serverWebpackConfig;
 };