Calculator v1.6: round-screen keypad with arithmetic

- 19-key layout fitted to round display, centered focus, scrollable list
- full arithmetic: +-*/ %, decimals, +/- , AC, divide-by-zero, chained ops
- scroll-to-center focus with top/bottom spacers, high-contrast keys
- tests: arithmetic + geometry/contrast

package.json

@@ -0,0 +1,15 @@
+{
+  "name": "xiaomi-vela-s4-hello-world",
+  "version": "1.0.0",
+  "private": true,
+  "description": "Minimal Xiaomi Vela JS Hello World app for Xiaomi Watch S4",
+  "scripts": {
+    "build": "aiot build",
+    "release": "aiot release",
+    "build:source-map": "aiot build --devtool=source-map",
+    "help": "aiot build -h"
+  },
+  "devDependencies": {
+    "aiot-toolkit": "2.0.5"
+  }
+}