Modernize process manager documentation

Replace outdated foreman-issues.md with comprehensive process-managers.md guide.

Changes:
- Create docs/building-features/process-managers.md with modern guidance
  - Documents both Overmind (recommended) and Foreman
  - Explains why React on Rails needs multiple processes
  - Includes authoritative explanation from Foreman's wiki about not bundling
  - Shows how bin/dev works under the hood
- Move docs/building-features/foreman-issues.md to docs/outdated/
  - Preserves 2017-era bug reports for historical reference
  - Removes clutter from main docs (outdated/ filtered from navigation)
- Update lib/react_on_rails/dev/process_manager.rb
  - Change link from our old doc to official Foreman wiki
  - Users get explanation directly from authoritative source

Addresses feedback that foreman-issues.md was outdated and didn't mention
modern alternatives like Overmind (which bin/dev actually prefers).

Author: ihabadham

docs/building-features/process-managers.md

@@ -0,0 +1,91 @@
+# Using Process Managers with React on Rails
+
+React on Rails requires running multiple processes simultaneously during development:
+
+- Rails server
+- Webpack dev server (client bundle)
+- Webpack watcher (server bundle)
+
+## Running Your Development Server
+
+React on Rails includes `bin/dev` which automatically uses Overmind or Foreman:
+
+```bash
+./bin/dev
+```
+
+This script will:
+
+1. Try to use Overmind (if installed)
+2. Fall back to Foreman (if installed)
+3. Show installation instructions if neither is found
+
+## Installing a Process Manager
+
+### Overmind (Recommended)
+
+Overmind provides easier debugging and better signal handling:
+
+```bash
+# macOS
+brew install overmind
+
+# Linux
+# See: https://github.com/DarthSim/overmind#installation
+```
+
+### Foreman (Alternative)
+
+Foreman is a widely-used Ruby-based process manager:
+
+```bash
+# Install globally (NOT in Gemfile)
+gem install foreman
+```
+
+**Important:** Do NOT add Foreman to your `Gemfile`. Install it globally on your system.
+
+**Why not in Gemfile?**
+
+From [Foreman's documentation](https://github.com/ddollar/foreman/wiki/Don't-Bundle-Foreman):
+
+> Foreman is not a library, and should not affect the dependency tree of your application.
+
+Key reasons:
+
+- **Dependency conflicts**: Including Foreman in your Gemfile can create dependency conflicts that break other projects
+- **Security risk**: Loading Foreman as an application dependency creates an unnecessary security vulnerability vector
+- **Stability**: Foreman is mature and stable; bundling it could introduce bugs from unnecessary dependency updates
+- **Wrong abstraction**: Foreman is a system tool, not an application dependency
+
+Install Foreman globally: `gem install foreman`
+
+## Alternative: Run Process Managers Directly
+
+You can also run process managers directly instead of using `bin/dev`:
+
+```bash
+# With Overmind
+overmind start -f Procfile.dev
+
+# With Foreman
+foreman start -f Procfile.dev
+```
+
+## Customizing Your Setup
+
+Edit `Procfile.dev` in your project root to customize which processes run and their configuration.
+
+The default `Procfile.dev` includes:
+
+```procfile
+rails: bundle exec rails s -p 3000
+wp-client: bin/shakapacker-dev-server
+wp-server: SERVER_BUNDLE_ONLY=true bin/shakapacker --watch
+```
+
+## See Also
+
+- [HMR and Hot Reloading](./hmr-and-hot-reloading-with-the-webpack-dev-server.md)
+- [Foreman documentation](https://github.com/ddollar/foreman)
+- [Overmind documentation](https://github.com/DarthSim/overmind)

docs/building-features/foreman-issues.md renamed to docs/outdated/foreman-issues.md

@@ -147,7 +147,7 @@ def show_process_manager_installation_help
             DO NOT add foreman to your Gemfile. Install it globally on your system.
 
             For more information about why foreman should not be in your Gemfile, see:
-            https://github.com/shakacode/react_on_rails/blob/master/docs/javascript/foreman-issues.md
+            https://github.com/ddollar/foreman/wiki/Don't-Bundle-Foreman
 
             After installation, try running this script again.
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