# WP-39 — Showcase: linked code snippets + teaching animations

Status: done
Phase: 8 — platform/DX/showcase
Priority: P1

## Outcome

`?raw` imports are NOT supported by Angular's esbuild build (verified), so anti-drift is done via
a generator (mirrors `gen:api`): `// #region showcase:<name>` markers in real source
(registration.ts, remote-data.ts, postcode.ts, change-request.machine.ts, intake.machine.ts) →
`scripts/gen-snippets.mjs` (`npm run gen:snippets`) → committed `src/app/showcase/snippets.generated.ts`.
A CI drift gate (`gen:snippets && git diff --exit-code`) forces a regen after any edit, so the shown
code IS the shipped code. The showcase renders the 5 real snippets (union/fold/parse/machine/steps)
each with a `↳ <source file>` caption, highlighted by a tiny dependency-free `highlightTs` (+spec);
the deliberately-wrong illustrations stay authored (no real source to link). Teaching animation: the
active state node pops (scale) as the wizard transitions, and the parse result animates in
(`animate.enter`), reusing the existing reduced-motion-safe toolkit. Generated file is
prettier-ignored (like api-client.ts) so the drift gate and format:check don't conflict.

## Why

The `/concepts` showcase shows live components, but its code snippets are hand-authored
`innerHTML` strings with manual highlighting — they drift from the real code. And the animation
toolkit (`withViewTransitions`, native `animate.enter/leave`, reduced-motion-safe keyframes in
`styles.scss`) is proven in dashboard/upload but unused for teaching motion.

## Decisions

- **Anti-drift snippets:** load _real_ source excerpts via Vite `?raw` imports with `// #region name`
  markers + a tiny pure extractor; render with lightweight highlighting. No more `innerHTML` literals.
- On the Storybook/MDX side, use `<Source>`/Canvas "show code" consistently (extend beyond the
  current 4 of 14 pages).
- **Reuse** the existing motion toolkit (no new animation lib): `animate.enter/leave` on the
  fold/union demos + a "step through `reduce`" animation for the TEA loop; keep reduced-motion-safe.

## Files

- `src/app/showcase/concepts.page.ts` — replace `innerHTML` snippets with `?raw`+region excerpts;
  apply animations.
- New tiny extractor util (pure) + spec (region slicing).
- `src/docs/machines.mdx`, `fp-in-ui.mdx`, `remote-data.mdx` — reference the live linked snippets.

## Acceptance criteria

- [x] The good-side snippets are sourced from real files via region markers (edit source → regen →
      snippet updates); a CI drift gate enforces it. Bad-pattern illustrations stay authored.
- [x] The state machine + parse demos animate (reduced-motion respected globally); no new dependency.
- [x] `npm run ci` green.