docs: say component tests are allowed, not absent by rule

CLAUDE.md read as a prohibition — "Vitest for its own pure helpers only, no
React, no DOM". It was only ever a description of what was installed, and it
was talking future contributors out of a test they are allowed to write.

Tests now states what exists, that component tests are allowed, and what the
first one costs: jsdom or happy-dom, @testing-library/react v16+ for React 19,
environment and a *.spec.tsx include. Notes that babel-plugin-react-compiler is
in devDependencies but not enabled in next.config.ts, so there is no transform
mismatch to work around.

Adds which to reach for. A decision belongs in a pure test, extracted into
components/{feature}/. A defect only a real render shows — ref-versus-state
timing, effect ordering — belongs in a component test, because no pure test can
see it. VoiceReviewSheet is the cheap first one; TreatmentWorkspace needs six
axios mocks and earns its keep only for a bug that needs it.

Same correction in vitest.config.ts's docblock and the spec's §12 line, which
each carried their own copy of "no React, no DOM".

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -39,7 +39,7 @@ There is **no root `package.json`**. Every npm command runs inside `backend/` or
 | `npx tsc --noEmit` | **Verification gate for any type or cross-cutting frontend change** |
 | `npm run build` | Production build (`output: 'standalone'`) |
 | `npm run lint` | ESLint via Next |
-| `npx vitest run` | Vitest — pure helpers only (`prosthesisTree.ts`, `voiceReviewRows.ts`, `toothSelectionGroups.ts`, `voiceApply.ts`) |
+| `npx vitest run` | Vitest — today the pure helpers in `components/treatment/*.spec.ts`; component tests are allowed, see **Tests** |
 
 `NEXT_PUBLIC_*` values are baked in at build time — restart `npm run dev` after changing `.env.local`.
 
@@ -104,7 +104,15 @@ Clinics may only dispatch to labs they are linked to: `OrganizationLink` (A↔B,
 
 ### Tests
 
-Jest covers pure logic only — permission normalization, phone/timezone helpers, task generation, lab-send validation, voice extraction contract (`backend/src/**`). Frontend has Vitest for its own pure helpers only — no React, no DOM: `prosthesisTree.ts`, `voiceReviewRows.ts`, `toothSelectionGroups.ts` and `voiceApply.ts` (`frontend/src/components/treatment/*.spec.ts`), run via `npx vitest run`. When a component callback holds a decision worth testing, extract the decision into `components/{feature}/` and leave the commit — state, refs, save order — in the component; `voiceApply.ts` is the worked example. `npx tsc --noEmit` remains the frontend's cross-cutting gate.
+Jest covers pure logic only — permission normalization, phone/timezone helpers, task generation, lab-send validation, voice extraction contract (`backend/src/**`).
+
+Frontend runs Vitest (`npx vitest run`). `npx tsc --noEmit` remains the cross-cutting gate.
+
+**What exists today** is pure-helper specs under `frontend/src/components/treatment/*.spec.ts` — `prosthesisTree.ts`, `voiceReviewRows.ts`, `toothSelectionGroups.ts`, `voiceApply.ts`. `vitest.config.ts` therefore sets no `environment` and includes `*.spec.ts` only.
+
+**Component tests are allowed.** Nothing here forbids them; the setup simply is not installed yet. Adding the first one means `jsdom` (or `happy-dom`) and `@testing-library/react`, plus `environment: 'jsdom'` and a `*.spec.tsx` include in `vitest.config.ts`. React 19 needs testing-library v16+. The React compiler babel plugin is in `devDependencies` but **not** enabled in `next.config.ts`, so there is no transform mismatch to work around.
+
+**Which to reach for.** Prefer a pure test when the thing under test is a decision: extract it into `components/{feature}/` and leave the commit — state, refs, save order — in the component. `voiceApply.ts` is the worked example, pulled out of a callback in `TreatmentWorkspace.tsx`. Reach for a component test when the defect is only visible in a real render — ref-versus-state timing, effect ordering, a callback firing before a re-render — because no pure test can see those. Start with a small, prop-driven component (`VoiceReviewSheet` is the easy first one); rendering `TreatmentWorkspace` means mocking next-intl, the i18n router and six axios modules, so it earns its keep only for a bug that needs it.
 
 ## Deployment
 

docs/specs/voice-treatment-entry/spec.md

@@ -1062,10 +1062,12 @@ enabling this for real clinics.
 - `cd backend && npm run prisma:migrate && npm run prisma:seed` — the new `CatalogEntityKind`
   values and their translation rows. The seed never wipes, so re-running it is safe.
 - `cd frontend && npx vitest run` — **new**. One dev dependency, one config, one script,
-  covering the pure helpers only: `prosthesisTree.ts` (stack legality, `applyLeafToJobs`
+  covering `prosthesisTree.ts` (stack legality, `applyLeafToJobs` precedence,
-  precedence, `toothRegionColors`) and `voiceReviewRows.ts` (row availability, the merged
+  `toothRegionColors`), `voiceReviewRows.ts` (row availability, the merged row, folding chips
-  row, folding chips into the result). No React, no DOM. `CLAUDE.md` is updated in the same
+  into the result), `toothSelectionGroups.ts` and `voiceApply.ts` (the apply decision).
-  commit — "there are no frontend tests" stops being true.
+  Pure functions, so no DOM environment is configured — a limit of what exists, not a rule
+  against component tests; `CLAUDE.md` > Tests says what adding one costs. `CLAUDE.md` is
+  updated in the same commit — "there are no frontend tests" stops being true.
 - `cd frontend && npx tsc --noEmit` — frontend type gate.
 - `cd frontend && npm run build` — production build.
 - ESLint on every touched file, no new warnings.

frontend/vitest.config.ts

@@ -2,8 +2,11 @@ import path from 'node:path';
 import { defineConfig } from 'vitest/config';
 
 /**
- * Covers the pure helpers only — no React, no DOM. `@/*` mirrors `tsconfig.json`'s path so a
+ * Covers the pure helpers, which is all that exists today — hence no `environment` and a
- * spec can import the same modules the app does.
+ * `*.spec.ts` include. Component tests are not ruled out: add jsdom, @testing-library/react,
+ * `environment: 'jsdom'` and `*.spec.tsx` here. See CLAUDE.md > Tests.
+ *
+ * `@/*` mirrors `tsconfig.json`'s path so a spec can import the same modules the app does.
  */
 export default defineConfig({
   resolve: {