Overhaul CI/CD, specs, and release pipeline

[Metalzoid]

Summary

Aligns modal_stack's infrastructure with the sibling swal_rails gem so both share the same support matrix and release pipeline.

• Multi-Rails CI — matrix Ruby 3.2 / 3.3 / 3.4 / 3.5 / 4.0 × Rails 7.2 / 8.0 / 8.1 / 8.1+sprockets via Appraisals (4 generated gemfiles/). Adds dedicated lint job and a ci-success aggregator for branch protection.
• JS jobs in CI — bun test, bun run build:check, and a bundle-freshness check that catches PRs editing JS source without rebuilding the importmap-friendly app/assets/javascripts/modal_stack.js.
• Automated release on push to main via OIDC trusted publishing (.github/workflows/release.yml). Tag, GitHub Release, and gem push driven by lib/modal_stack/version.rb.
• Spec infra — fleshed-out dummy Rails app (controllers, views, routes, importmap, sprockets manifest) + Cuprite rails_helper.rb. Full Capybara system suite under spec/system/ covering boot, push, pop (ESC + backdrop), depth-2 stack inertness, modal_replace with history: :push, browser back, all four drawer sides, and the dismissible flag.
• RuboCop — adopts the swal_rails-style baseline (Metrics tuned for DSL helpers, Naming/PredicatePrefix exempt for the Capybara matchers, ParameterLists ignores keyword args). .rubocop_todo.yml deleted; residual offenses fixed in source (modal_link_to refactored into helpers; HTML fixtures hoisted out of the RSpec.describe block).
• Bug fix bundled — capybara_spec now uses an around block to restore Capybara.app / current_driver so the unit specs stop polluting global state and breaking system specs that run after them.
• Misc — Dependabot (bundler + github-actions, weekly), README rewritten with usage / dev / release sections, CHANGELOG reformatted to Keep a Changelog, gemspec exclusions extended (Appraisals, gemfiles/, examples/, CLAUDE.md, bunfig.toml).

Local verification

• bundle exec rake (rspec + rubocop) green on all 4 appraisals — 105 examples, 0 failures, 38 files / no offenses each.
• bun test — 61 pass / 0 fail.
• bun run build:check clean.
• bin/build && git diff --exit-code app/assets/javascripts/modal_stack.js — no drift.
• gem build modal_stack.gemspec produces a 0.1.0 gem with only app/, lib/, CHANGELOG.md, CODE_OF_CONDUCT.md, LICENSE.txt, Rakefile, README.md (no bin/, spec/, gemfiles/, Appraisals, examples/, .github/, CLAUDE.md).

Test plan

• All 19 matrix jobs (5 Ruby × 4 gemfile − Ruby 4.0 × Rails 7.2 exclusion) green.
• lint, js-test, js-build-check, bundle-freshness, ci-success green.
• After merge: confirm release.yml tags v0.1.0 (no-op since tag already exists) without errors.

Notes

• Includes the orphan commit e22f2a7 from PR Force RuboCop to use the repository config in rake tasks #2 (Force RuboCop to use the repository config in rake tasks). The new CI calls bundle exec rubocop --no-server directly, so the rake-level override is no longer needed — this PR restores bare RuboCop::RakeTask.new. Merging this PR also closes out PR Force RuboCop to use the repository config in rake tasks #2.
• Trusted Publishing for modal_stack is already configured on rubygems.org, per user confirmation. The release workflow will publish on the next push to main after merge if the version bumps.

🤖 Generated with Claude Code