Update i18n.md to explain bin/dev precompile_hook coordination

References the idempotent locale generation feature (PR #2093) and
explains how bin/dev automatically coordinates the precompile hook.

Author: justin808

docs/building-features/i18n.md

@@ -21,10 +21,31 @@ You can use [Rails internationalization (i18n)](https://guides.rubyonrails.org/i
 
 3. The locale files must be generated before `yarn build` using `rake react_on_rails:locale`.
 
-   For development, you should adjust your startup scripts (`Procfile`s) so that they run `bundle exec rake react_on_rails:locale` before running any Webpack watch process (`yarn run build:development`).
+   **Recommended: Use Shakapacker's precompile_hook with bin/dev** (React on Rails 16.2+, Shakapacker 9.3+)
 
-   If you are not using the React on Rails test helper,
-   you may need to configure your CI to run `bundle exec rake react_on_rails:locale` before any Webpack process as well.
+   The locale generation task is idempotent and can be safely called multiple times. Configure it in Shakapacker's `precompile_hook` and `bin/dev` will handle coordination automatically:
+
+   ```yaml
+   # config/shakapacker.yml
+   default: &default
+     # Run locale generation before webpack compilation
+     # Safe to run multiple times - will skip if already built
+     precompile_hook: 'bundle exec rake react_on_rails:locale'
+   ```
+
+   With this configuration, `bin/dev` will:
+
+   - Run the precompile hook **once** before starting development processes
+   - Set `SHAKAPACKER_SKIP_PRECOMPILE_HOOK=true` to prevent duplicate execution
+   - Pass the environment variable to all spawned processes (Rails, webpack, etc.)
+
+   This eliminates the need for sleep hacks and manual coordination in `Procfile.dev`. See the [Process Managers documentation](./process-managers.md#precompile-hook-integration) for details.
+
+   **Alternative: Manual coordination**
+
+   For development, you can adjust your startup scripts (`Procfile`s) so that they run `bundle exec rake react_on_rails:locale` before running any Webpack watch process (`yarn run build:development`).
+
+   If you are not using the React on Rails test helper, you may need to configure your CI to run `bundle exec rake react_on_rails:locale` before any Webpack process as well.
 
    > [!NOTE]
    > If you try to lint before running tests, and you depend on the test helper to build your locales, linting will fail because the translations won't be built yet.