Set up Vitest + 22 smoke tests on pure modules (proposal #6)

Phase 3 of the refactor plan in docs/ARCHITECTURE.md — the foundation
that unblocks every safe refactor below.

Install
- yarn add -D vitest@3 jsdom @testing-library/dom @testing-library/react
  @testing-library/jest-dom

Note: pinned to vitest@3 (not the latest 4.x) because yarn 1's peer
resolution breaks on vitest@4's peer link to vite. With vitest@3 the
existing Vite 8 install resolves cleanly.

Configuration
- vitest.config.mts (new): separate from vite.config.mjs because the
  dev/build config wires up renderer SDK aliases that point at sibling
  working trees (../renderer, ../Nitro_Render_V3). Tests are written
  against pure modules that don't pull in the renderer, so the test
  runner uses a smaller alias set.
- tests/setup.ts (new): imports @testing-library/jest-dom/vitest so
  custom matchers (toBeInTheDocument, etc.) are available without
  per-file imports.
- tsconfig.json: include "tests" so eslint stops complaining about
  unparseable files; also makes the IDE see the test files.
- package.json scripts: "test" (one-shot) and "test:watch".

Tests
- tests/WiredCreatorTools.helpers.test.ts (18 cases): covers the pure
  helpers extracted in 3c68d97 — createEmptyMonitorSnapshot,
  formatMonitorLatestOccurrence (5 time-bucket branches),
  formatMonitorHistoryOccurrence, formatVariableTimestamp,
  formatMonitorSource (4 branches), normalizeMonitorReason. These are
  the most boring-but-easy-to-break functions; locking them down first
  is high value, near-zero risk.
- tests/navigatorRoomCreatorStore.test.ts (4 cases): exercises the
  Zustand store added in the previous commit — initial state, latch
  semantics, 5s auto-reset (with fake timers), and the
  "second beginCreate restarts the lockout" invariant. Validates that
  the store-based replacement of the let-singleton has the same
  observable behavior, plus the new invariant that wasn't possible
  before (timer composition under StrictMode double-mount).

Side effect: two non-test source files were converted to `import type`
to keep the test bundle from accidentally pulling in the renderer SDK
transitively:
- src/components/wired-tools/WiredCreatorTools.types.ts
  (`import type { AvatarInfoFurni }`)
- src/components/wired-tools/WiredCreatorTools.helpers.ts
  (`import type { HotelDateTimeParts, MonitorSnapshot }`)
This is harmless — TypeScript already treated them as type-only —
and improves tree-shaking on build as a side benefit.

Verification
- yarn test -> 2 files, 22 tests passing in ~1.0s.
- yarn eslint on tests/ + the two type-only-import files: 0 errors,
  0 warnings.

Migration path
- Next adoption targets: cover useDoorbellState reducer (data hook
  split), the new useNitroQuery adapter (timeout/cleanup behavior),
  and the smaller pure formatters under src/api/.
- React component tests (via @testing-library/react) deferred until
  there's a small mock layer for the renderer SDK. The
  @testing-library/* deps are already installed so that PR is
  unblocked.

https://claude.ai/code/session_01GrR87LAqnAEyKG2ZbmQt5Q

package.json

@@ -9,7 +9,9 @@
         "build": "vite build && node scripts/minify-dist.mjs",
         "build:prod": "npx browserslist@latest --update-db && yarn build",
         "eslint": "eslint ./src",
-        "typecheck": "tsgo --noEmit"
+        "typecheck": "tsgo --noEmit",
+        "test": "vitest run",
+        "test:watch": "vitest"
     },
     "dependencies": {
         "@babel/runtime": "^7.29.2",
@@ -35,6 +37,9 @@
     "devDependencies": {
         "@tailwindcss/forms": "^0.5.11",
         "@tailwindcss/postcss": "^4.2.4",
+        "@testing-library/dom": "^10.4.1",
+        "@testing-library/jest-dom": "^6.9.1",
+        "@testing-library/react": "^16.3.2",
         "@types/node": "^25.6.0",
         "@types/react": "^19.2.14",
         "@types/react-dom": "^19.2.3",
@@ -47,12 +52,14 @@
         "eslint-plugin-react": "^7.37.5",
         "eslint-plugin-react-compiler": "19.1.0-rc.2",
         "eslint-plugin-react-hooks": "^7.1.1",
+        "jsdom": "^29.1.1",
         "postcss": "^8.5.12",
         "postcss-nested": "^7.0.2",
         "sass": "^1.99.0",
         "tailwindcss": "^4.2.4",
         "typescript": "^6.0.3",
         "typescript-eslint": "^8.59.1",
-        "vite": "^8.0.10"
+        "vite": "^8.0.10",
+        "vitest": "^3"
     }
 }