Fix: Foreman execution fails in bundler context

[AbanoubGhadban]

Problem

The dummy app's bin/dev script fails with the following error when foreman is not included in the Gemfile:

can't find executable foreman for gem foreman. foreman is not currently included in the bundle, perhaps you meant to add it to your Gemfile? (Gem::Exception)

However, running foreman start -f Procfile.dev directly works fine.

Root Cause

1. Foreman is intentionally NOT included in the Gemfile (following React on Rails best practices documented in docs/javascript/foreman-issues.md)
2. Bundler intercepts system calls when binstubs are active, trying to find foreman within the current bundle context
3. The ReactOnRails process manager calls system("foreman", "start", "-f", procfile) which gets intercepted by bundler

Available Solutions

1. Add foreman to Gemfile - Goes against documented best practices
2. Use full path to system foreman - Brittle and platform-dependent
3. Clear bundle environment - Complex and error-prone
4. Use Bundler.with_unbundled_env - Clean, purpose-built solution

Chosen Solution

Implement a fallback strategy in ProcessManager:

1. First attempt: Try running foreman within bundler context (for projects that do include foreman)
2. Fallback: Use Bundler.with_unbundled_env to run system foreman if bundler context fails
3. Clear error messaging: If foreman isn't found in either context, provide helpful guidance

Implementation Plan

• Modify lib/react_on_rails/dev/process_manager.rb with intelligent fallback
• Add comprehensive error messaging with links to documentation
• Add tests for the fallback mechanism
• Ensure compatibility with both bundled and system foreman installations

Benefits

• Maintains best practices: Keeps foreman out of Gemfile
• Backwards compatible: Works with projects that do include foreman
• Better UX: Clear error messages guide users to proper setup
• Robust: Handles both bundled and system foreman installations