workspace: pnpm monorepo with api, web, shared

TypeScript 7 strict, ESLint + Prettier, vitest, AGPL-3.0 license.
Decision 0001 records the latest-majors choice and the TS 6 alias.

Task: M0-T1

packages/shared/package.json

@@ -0,0 +1,18 @@
+{
+  "name": "@selfphoneng/shared",
+  "version": "0.0.0",
+  "private": true,
+  "license": "AGPL-3.0-or-later",
+  "type": "module",
+  "exports": {
+    ".": {
+      "types": "./src/index.ts",
+      "development": "./src/index.ts",
+      "default": "./dist/index.js"
+    }
+  },
+  "scripts": {
+    "build": "tsc -p tsconfig.build.json",
+    "typecheck": "tsc --noEmit"
+  }
+}