Phase 2: domain layer with tests

Vite + React + TypeScript + Vitest. No router, state library or UI kit.

The 159-row combo table is extracted from reference/index.html by
scripts/extract-reference-data.mjs rather than retyped: it balances
brackets past string literals to slice out the pure-data declarations and
evaluates them in a vm with no DOM. raw.ts and labels.ts are generated.
The extracted count matches the 159 the Phase 1 app reported on device.

Entry.id keeps the reference's format verbatim (shift>p1@S#FIX VEL),
built from the unsplit context string, so drill progress already on the
phone migrates instead of being orphaned.

The domain is pure where the reference was not: boxes go in and new
boxes come out, and the random source is injected. That is what made
card selection testable.

Two bugs found by doing so:

- pickCard returned the card just answered when random() gave exactly 0.
  A zero-weight card does not move the accumulator, so "r <= 0" matched
  it. The reference has this; at one draw in 2^53 it is invisible in use,
  but a pinned random source hits it every time. Fixed to "r < 0".
- boxDistribution incremented through an index that
  noUncheckedIndexedAccess types as possibly undefined.

65 tests. Several assert numbers observed on the device: 159 entries,
sample-mode layers of 3 / 35 / 2, a 16-card SHIFT+pads deck.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

package.json

@@ -2,6 +2,7 @@
   "name": "sp404-layers",
   "version": "1.0.0",
   "private": true,
+  "type": "module",
   "description": "SP-404MK2 combo trainer, wrapped as an Android app",
   "scripts": {
     "sync:www": "bash scripts/sync-www.sh",
@@ -13,16 +14,28 @@
     "device:sleep-normal": "bash scripts/device.sh sleep-normal",
     "device:launch": "bash scripts/device.sh launch",
     "run:android": "npm run apk && npm run install:apk && npm run device:launch",
-    "logcat": "adb logcat -s Capacitor:V Capacitor/Console:V chromium:V"
+    "logcat": "adb logcat -s Capacitor:V Capacitor/Console:V chromium:V",
+    "test": "vitest run",
+    "test:watch": "vitest",
+    "typecheck": "tsc --noEmit",
+    "extract:data": "node scripts/extract-reference-data.mjs"
   },
   "dependencies": {
     "@capacitor/android": "^8.5.2",
     "@capacitor/app": "^8.1.1",
     "@capacitor/core": "^8.5.2",
     "@capacitor/haptics": "^8.0.2",
-    "@capacitor/preferences": "^8.0.1"
+    "@capacitor/preferences": "^8.0.1",
+    "react": "^19.3.0",
+    "react-dom": "^19.3.0"
   },
   "devDependencies": {
-    "@capacitor/cli": "^8.5.2"
+    "@capacitor/cli": "^8.5.2",
+    "@types/react": "^19.3.0",
+    "@types/react-dom": "^19.3.0",
+    "@vitejs/plugin-react": "^6.1.1",
+    "typescript": "^7.0.2",
+    "vite": "^8.3.0",
+    "vitest": "^5.0.1"
   }
 }