Switch from create-elm-app to Parcel and add CI/CD workflows

[adamnfish]

• Replace create-elm-app with Parcel 2 + @parcel/transformer-elm
• Add GitHub Actions deploy workflow (Pages artifact, not docs/ branch)
• Add CI workflow running elm-test on PRs and pushes to main
• Remove service worker
• Remove committed docs/ build output
• Update elm.json: elm 0.19.1, elm/core 1.0.5, elm-explorations/test 2.0.0
• Add local dev instructions to README

[Copilot]

Pull request overview

Migrate the Elm app build/deploy setup from create-elm-app (with committed docs/ output + service worker) to Parcel 2, and add GitHub Actions workflows for CI (elm-test) and GitHub Pages deployment via the Pages artifact flow.

Changes:

• Replace CRA-era bootstrapping (service worker, %PUBLIC_URL% assets, public/ manifest) with Parcel-oriented src/index.html + module entrypoint.
• Add CI workflow running Elm tests and deploy workflow publishing the Parcel dist/ output to GitHub Pages.
• Remove committed build artifacts under docs/ and remove service worker setup.

Reviewed changes

Copilot reviewed 16 out of 26 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/registerServiceWorker.js	Removed service worker registration code.
src/index.js	Removed service worker import/registration; keeps Elm init.
src/index.html	Updated asset paths and added module script entrypoint for Parcel.
src/manifest.json	Added web app manifest under src/.
src/favicon.ico	Added favicon in src/ to be bundled by Parcel.
public/manifest.json	Removed old manifest location used by create-elm-app.
elmapp.config.js	Removed create-elm-app config.
elm.json	Updated Elm/test dependency versions and indirect test deps.
package.json	Added Parcel/Elm tooling scripts and dev dependencies.
docs/static/js/vendors~main.7b45496b.chunk.js.map	Removed committed build artifact.
docs/static/js/vendors~main.7b45496b.chunk.js	Removed committed build artifact.
docs/static/js/runtime~main.538a88e8.js.map	Removed committed build artifact.
docs/static/js/runtime~main.538a88e8.js	Removed committed build artifact.
docs/static/js/main.7ba80f70.chunk.js	Removed committed build artifact.
docs/static/css/main.f98b609c.chunk.css.map	Removed committed build artifact.
docs/static/css/main.f98b609c.chunk.css	Removed committed build artifact.
docs/service-worker.js	Removed committed service worker artifact.
docs/index.html	Removed committed build artifact entry HTML.
docs/asset-manifest.json	Removed committed build artifact manifest.
README.md	Updated Pages URL and added local dev/build/test instructions.
.gitignore	Ignored Parcel outputs (dist/, .parcel-cache/).
.github/workflows/deploy.yml	Added GitHub Pages build+deploy workflow.
.github/workflows/ci.yml	Added CI workflow running Elm tests.

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