WA-RAILS7-019: Webpacker removal strategy

[kitcommerce]

Summary

Rails 7 removed Webpacker. Workarea uses Sprockets 4 (landed in PR #740), but storefronts using Webpacker need a migration path.

Approach

1. Audit current Webpacker usage in core/admin/storefront
2. Document Sprockets 4 as the recommended path (already landed)
3. For apps requiring modern JS tooling, document jsbundling-rails + esbuild integration
4. Provide migration guide for Webpacker → Sprockets or Webpacker → jsbundling

Objective

Clear documentation for storefront apps on JS bundling post-Rails 7.

Client Impact

Informational. Clients on Webpacker need guidance before Rails 7 upgrade.

Acceptance Criteria

• Audit finds all Webpacker references (if any)
• Migration guide written: Webpacker → Sprockets 4
• Optional: jsbundling-rails integration guide
• Added to docs/rails7-migration-patterns/

Verification Plan

Review guide with a sample storefront app using Webpacker.

[kitcommerce]

Audit results:

• Searched core/, admin/, and storefront/ for webpacker / webpack references: none found.
• Remaining references were limited to documentation/templates (e.g. --skip-webpack-install).

What I did:

• Added Rails 7 migration docs under docs/rails7-migration-patterns/:
  • Webpacker → Sprockets 4 (recommended)
  • Optional jsbundling-rails (esbuild) + Sprockets
• Updated docs + plugin_template.rb to use --skip-javascript instead of --skip-webpack-install.

PR: #757

[kitcommerce]

Merged via PR #757.