Extract engine from citation-evidence umbrella (CENG-WP-0001)

Bootstrap @citation-evidence/engine as a standalone TypeScript package
with shared types and engine services copied from the umbrella MVP.
All 89 tests pass with lint and typecheck clean.

package.json

@@ -0,0 +1,33 @@
+{
+  "name": "@citation-evidence/engine",
+  "version": "0.1.0",
+  "private": true,
+  "description": "Core domain model and engine services for the citation-evidence ecosystem.",
+  "license": "Apache-2.0",
+  "type": "module",
+  "packageManager": "pnpm@9.15.0",
+  "engines": {
+    "node": ">=20.10.0"
+  },
+  "exports": {
+    ".": "./src/engine/index.ts",
+    "./shared": "./src/shared/index.ts"
+  },
+  "scripts": {
+    "test": "vitest run",
+    "test:watch": "vitest",
+    "lint": "eslint .",
+    "typecheck": "tsc -b --noEmit"
+  },
+  "devDependencies": {
+    "@types/node": "^20.14.0",
+    "eslint": "^9.7.0",
+    "eslint-import-resolver-typescript": "^3.6.3",
+    "eslint-plugin-boundaries": "^4.2.2",
+    "eslint-plugin-import": "^2.30.0",
+    "globals": "^15.9.0",
+    "typescript": "^5.5.4",
+    "typescript-eslint": "^8.0.0",
+    "vitest": "^2.0.5"
+  }
+}