[codex] Make hearting optimistic and animated in every context

[zachlatta]

Summary

• Adds a Stimulus like controller so devlog hearts update optimistically, animate immediately, and persist with JSON requests instead of navigating/reloading inside feed/profile/project/devlog contexts.
• Keeps the no-JS/Turbo Stream fallback intact while rendering both outline and filled hearts for instant state changes.
• Namespaces the filled-heart SVG gradient per likeable record so multiple liked hearts on one page render correctly.
• Adds controller coverage for JSON create/destroy responses and the existing Turbo Stream response.

Scope guard

This branch is rebuilt from current origin/main and intentionally excludes the unrelated improved-agent-experience commits. Checked absent from codex/heart-animation-messaging: bca38f86, 0799caf6, 18f39f9b.

Changed files are limited to the like implementation/tests; the flow GIFs below are hosted on cdn.hackclub.com.

AGENTS.md / repo conventions

• No DB migrations, schema changes, generators, admin surfaces, PaperTrail audit flows, encrypted fields, or Lockbox/blind-index changes are involved.
• Authorization remains through the existing LikePolicy; the JSON response path is added inside the already-authorized create/destroy actions.
• Tests use Minitest under test/controllers; no RSpec was added.
• Frontend code stays in app/javascript/controllers and is registered through the Stimulus manifest used by the esbuild pipeline.
• SCSS stays on the existing BEM-style .like-button block, uses classes instead of inline styles, and references Stardance CSS variables / brand tokens rather than new hardcoded theme colors.
• The existing like partial and Turbo Stream fallback are reused instead of replacing the whole like system; no Flavortown styling or dead code is carried forward.
• GIF evidence is hosted on Hack Club CDN; no CDN key or generated binary artifact is stored in the repo.

Validation

• git diff --check origin/main...HEAD
• RAILS_ENV=test DATABASE_URL=postgresql://postgres:pass@localhost:5432/stardance_test mise exec ruby@ruby-3.4.3 -- bin/rails test test/controllers/likes_controller_test.rb
• mise exec ruby@ruby-3.4.3 -- bundle exec rubocop app/controllers/likes_controller.rb app/helpers/likes_helper.rb test/controllers/likes_controller_test.rb
• mise exec ruby@ruby-3.4.3 -- bundle exec erb_lint app/views/likes/_button.html.erb
• ./node_modules/.bin/prettier --check app/javascript/controllers/like_controller.js app/javascript/controllers/index.js app/assets/stylesheets/components/_like_button.scss
• npm exec -- esbuild app/javascript/application.js --bundle --sourcemap --format=esm --outdir=/tmp/stardance-heart-build --public-path=/assets
• Playwright/Chrome runtime verification against local Rails test server: home feed, project page, profile feed, and devlog detail each POSTed /devlogs/:id/like, stayed on the same URL, set aria-pressed="true", applied the liked class, and showed count 1.
• Each CDN GIF URL below was verified as 200 image/gif.

Note: Rails boot emitted the existing local MJML 5 binary warning during test/server commands.

Flow GIFs

Home feed

Project page

Profile feed

Devlog detail