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>

tsconfig.json

@@ -0,0 +1,22 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "lib": ["ES2022", "DOM", "DOM.Iterable"],
+    "module": "ESNext",
+    "moduleResolution": "bundler",
+    "jsx": "react-jsx",
+
+    "strict": true,
+    "noUncheckedIndexedAccess": true,
+    "noImplicitOverride": true,
+    "noFallthroughCasesInSwitch": true,
+    "exactOptionalPropertyTypes": true,
+
+    "verbatimModuleSyntax": true,
+    "isolatedModules": true,
+    "resolveJsonModule": true,
+    "skipLibCheck": true,
+    "noEmit": true
+  },
+  "include": ["src"]
+}