Modernize JavaScript build toolchain

[tagliala]

Replace Rollup with Rolldown v1 for bundling (10-30x faster builds). The new config lives in rolldown.config.mjs and the build script is updated accordingly.

Replace ESLint + neostandard with Oxlint v1 for linting (50-100x faster). The new config lives in .oxlintrc.json and is run via pnpm lint. Use args: none on no-unused-vars to skip unused function parameters, which serve as API documentation for callback signatures. Rename .github/workflows/eslint.yml to lint.yml accordingly.

These choices are informed by ongoing upstream discussions about how best to align the neostandard and Rollup ecosystems with modern JavaScript tooling (neostandard/neostandard#350, rollup/plugins#2010).

Drop Babel — transpilation is now handled by Rolldowns built-in Oxc transforms. The minimum browser targets are unchanged (Chrome 60+, Firefox 60+, iOS 12+, Safari 12+).

Remove 9 unused npm devDependencies (@babel/core, @babel/preset-env, @rollup/plugin-babel, @rollup/plugin-node-resolve, eslint, eslint-plugin-compat, neostandard, rollup, rollup-plugin-copy).

Clean up .gitignore (remove stale !.babelrc negation) and update Rakefile lint task to call the new pnpm lint script instead of pnpm eslint.

Drop CSV < 25 compatibility and bump gem version to 19.0.0.

[Copilot]

Pull request overview

This PR modernizes the project’s JavaScript toolchain by migrating bundling from Rollup to Rolldown and linting from ESLint/neostandard to Oxlint, while also bumping the gem and dependency compatibility to align with client_side_validations v25 and dropping CSV < 25 compatibility.

Changes:

• Replace Rollup + Babel pipeline with Rolldown v1 and update generated dist/vendor bundles.
• Replace ESLint/neostandard with Oxlint and update CI + Rake tasks to run the new linter.
• Bump gem/package versions to 19.0.0 and update Ruby/Gemfile appraisal matrix for CSV 25.

Reviewed changes

Copilot reviewed 15 out of 22 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
vendor/assets/javascripts/rails.validations.simple_form.js	Regenerated vendored UMD bundle with Rolldown output and updated version banner.
vendor/assets/javascripts/rails.validations.simple_form.bootstrap4.js	Regenerated vendored Bootstrap 4+ UMD bundle with Rolldown output and updated version banner.
rollup.config.mjs	Removed Rollup configuration as bundling migrates to Rolldown.
rolldown.config.mjs	Added Rolldown config, including banner normalization and vendor copy steps.
Rakefile	Updated JS lint task to call pnpm lint instead of the removed pnpm eslint.
package.json	Switched build to Rolldown, introduced Oxlint script, and removed Rollup/Babel/ESLint-related dev deps; bumped version + peer dependency.
lib/client_side_validations/simple_form/version.rb	Bumped gem version to 19.0.0.
gemfiles/csv_25.0.gemfile	Updated appraisal Gemfile to target client_side_validations ~> 25.0.
eslint.config.mjs	Removed ESLint configuration as linting migrates to Oxlint.
dist/simple-form.js	Regenerated dist UMD bundle via Rolldown with updated version banner.
dist/simple-form.esm.js	Regenerated dist ESM bundle via Rolldown with updated version banner.
dist/simple-form.bootstrap4.js	Regenerated dist Bootstrap 4+ UMD bundle via Rolldown with updated version banner.
dist/simple-form.bootstrap4.esm.js	Regenerated dist Bootstrap 4 ESM bundle (note: banner text needs correction).
client_side_validations-simple_form.gemspec	Bumped runtime dependency to client_side_validations >= 25.0.
CHANGELOG.md	Added 19.0.0 entry documenting breaking changes and toolchain migration.
Appraisals	Updated appraisal definition from CSV 24 to CSV 25.
.oxlintrc.json	Added Oxlint configuration (including no-unused-vars args handling).
.gitignore	Removed stale .babelrc negation after dropping Babel.
.github/workflows/ruby.yml	Updated CI matrix to run against CSV 25 appraisal.
.github/workflows/lint.yml	Updated workflow naming/job and switched to pnpm lint.
.github/dependabot.yml	Removed Babel dependency update grouping (Babel removed).
.babelrc	Removed Babel config (Babel removed).

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[Copilot]

Pull request overview

Copilot reviewed 15 out of 22 changed files in this pull request and generated no new comments.