Add shakapacker-config binstub for Shakapacker 9.2.0

Add the new bin/shakapacker-config utility introduced in Shakapacker 9.2.0
to all dummy apps. This tool exports webpack/rspack configurations in
human-readable formats for debugging and comparison.

The binstub provides:
- --doctor mode for comprehensive troubleshooting
- --save mode to export configurations
- Multiple output formats (YAML, JSON, inspect)
- Support for both webpack and rspack

Added to:
- spec/dummy/bin/shakapacker-config
- react_on_rails_pro/spec/dummy/bin/shakapacker-config
- react_on_rails_pro/spec/execjs-compatible-dummy/bin/shakapacker-config

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

Co-Authored-By: Claude <[email protected]>

Author: justin808

react_on_rails_pro/spec/dummy/bin/shakapacker-config

@@ -0,0 +1,11 @@
+#!/usr/bin/env node
+
+// Minimal shim - all logic is in the TypeScript module
+const { run } = require("shakapacker/configExporter")
+
+run(process.argv.slice(2))
+  .then((exitCode) => process.exit(exitCode))
+  .catch((error) => {
+    console.error(error.message)
+    process.exit(1)
+  })

react_on_rails_pro/spec/execjs-compatible-dummy/bin/shakapacker-config

@@ -0,0 +1,11 @@
+#!/usr/bin/env node
+
+// Minimal shim - all logic is in the TypeScript module
+const { run } = require("shakapacker/configExporter")
+
+run(process.argv.slice(2))
+  .then((exitCode) => process.exit(exitCode))
+  .catch((error) => {
+    console.error(error.message)
+    process.exit(1)
+  })

spec/dummy/bin/shakapacker-config

@@ -0,0 +1,11 @@
+#!/usr/bin/env node
+
+// Minimal shim - all logic is in the TypeScript module
+const { run } = require("shakapacker/configExporter")
+
+run(process.argv.slice(2))
+  .then((exitCode) => process.exit(exitCode))
+  .catch((error) => {
+    console.error(error.message)
+    process.exit(1)
+  })