Modernize CI/test runner via Appraisal (mirrors u-case)

[serradura]

Summary

Brings the kind gem's test runner up to par with the modernized u-case + u-attributes gems.

CI matrix

• Ruby: 2.7, 3.0, 3.1, 3.2, 3.3, 3.4, 4.0, head
• ActiveModel: 6.0, 6.1, 7.0, 7.1, 7.2, 8.0, 8.1, edge (via Appraisal, gated per Ruby version)
• Each job runs:
  • Baseline (no activemodel)
  • Per-module isolation tests (KIND_BASIC=t) + KIND_STRICT=t strict_disabled_test
  • Each applicable Rails appraisal

Infrastructure

• Replaces bin/test + bin/prepare_coverage + the ENV-switched Gemfile with an Appraisals file and a generated gemfiles/rails_X_Y.gemfile layout.
• Adds bin/setup, bin/matrix, and rake matrix / rake test_basic_modules tasks. The basic-modules task uses Rake's rake_test_loader.rb so it works under /bin/sh (no shell brace expansion required).
• Workflow hardening (zizmor): explicit least-privilege permissions: { contents: read } and actions/checkout with persist-credentials: false.
• Coverage upload swapped from CodeClimate to Qlty (token auth via QLTY_COVERAGE_TOKEN).
• README badges swapped to Qlty equivalents; Ruby/Rails badges refreshed to >= 2.7 / >= 6.0.

Gemspec

• required_ruby_version bumped from >= 2.1.0 → >= 2.7.0.
• appraisal ~> 2.5 added as a development dependency.
• changelog_uri metadata wired up.

Source change — lib/kind/any.rb
Ruby 4.0 changed Set#inspect from "#<Set: {:low, :high}>" to "Set[:low, :high]", which broke the regex-based stripping in Kind::Any#name. The replacement rebuilds the brace-list form directly from @values so the output stays Kind::Any{:low, :high} on every supported Ruby.

Test fixes for Ruby 3.4+/4.0 compatibility

• Quote-agnostic regex for the private/protected method error message change (`b' → 'b'; for #<Foo> → for an instance of Foo).
• Hash#inspect format change in Ruby 3.4 ({:foo=>:bar} → {foo: :bar}): hardcoded error-message strings replaced with "#{hash.inspect} ..." interpolation so the assertion follows the runtime.

Manual setup needed on your side

1. Create the project at qlty.sh under serradura/kind.
2. Add QLTY_COVERAGE_TOKEN to the repo's GitHub Actions secrets (same flow as u-case).
3. Optionally remove the legacy CC_TEST_REPORTER_ID secret if still present.

Test plan

• CI passes the full 8-Ruby × N-Rails matrix
• Locally verified on Ruby 4.0.1: baseline (196 tests) + all KIND_BASIC modules + rails-8-1 + rails-edge all green
• Qlty badge resolves after merge to main

🤖 Generated with Claude Code