Add interactive Rails embeds and chapter animations

[victor-fdez]

Summary

• add beat-backed chapters with deterministic progress/state, stable transport commands, and player events
• add a framework-independent animate_it_embed custom element with responsive variants, poster-first readiness, visibility lifecycle, and accessible host controls
• add headless HAML/ERB chapter builders plus an optional pill/carousel preset for pills, cards, tabs, thumbnails, steppers, and custom SVG
• preserve animate_it_player, track schema v2, AnimateItTransport, Studio, and render compatibility
• publish Animate It 0.5.0 with curated changelog descriptions on every GitHub release

API

beat :review, at: 228, length: 132
chapter :review, beat: :review, label: "Review"

= animate_it_embed(
  "home-hiring-flow",
  poster: image_path("desktop.webp"),
  variants: [{
    media: "(max-width: 767px)",
    composition: "home-hiring-flow-mobile",
    poster: image_path("mobile.webp")
  }],
  navigation: { preset: :pills, mobile: :carousel },
  load_when_visible: 0.25,
  play_when_visible: 2.0 / 3,
  reduced_motion: :poster
)

Screenshots

Desktop

Mobile

Security and compatibility

• public playback remains explicitly allowlisted with default props only
• iframe commands use source-checked, same-origin messages
• Studio, frame, props, and render endpoints remain unavailable in production
• player manifests contain no application session data
• animate_it_player remains the unchanged low-level iframe helper
• AnimateItTransport remains a compatibility alias
• no track-schema version bump

Verification

• main RSpec suite: 128 examples, 0 failures
• Chromium/FFmpeg render smoke: 6 examples, 0 failures
• Rails 7.2 appraisal: 128 examples, 0 failures
• Rails 8.1 appraisal: 128 examples, 0 failures
• release-description/package specs: 4 examples, 0 failures
• RuboCop: 82 files, no offenses
• Brakeman: 0 medium/high warnings
• Bundler Audit: no vulnerabilities in main or either appraisal
• gem build and npm package dry run: successful

Release

After merge, the release workflow gates publication on the full CI suite, publishes animate_it 0.5.0 through RubyGems trusted publishing, creates v0.5.0, and creates a GitHub release from the curated CHANGELOG.md entry. Missing or empty release descriptions fail before publication.