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.

tsconfig.json

@@ -0,0 +1,29 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "lib": ["ES2022", "DOM"],
+    "module": "ESNext",
+    "moduleResolution": "Bundler",
+    "strict": true,
+    "noImplicitOverride": true,
+    "noFallthroughCasesInSwitch": true,
+    "noUncheckedIndexedAccess": true,
+    "exactOptionalPropertyTypes": true,
+    "noUnusedLocals": true,
+    "noUnusedParameters": true,
+    "noEmit": true,
+    "esModuleInterop": true,
+    "forceConsistentCasingInFileNames": true,
+    "isolatedModules": true,
+    "skipLibCheck": true,
+    "resolveJsonModule": true,
+    "verbatimModuleSyntax": true,
+    "baseUrl": ".",
+    "paths": {
+      "@shared/*": ["src/shared/*"],
+      "@engine/*": ["src/engine/*"]
+    }
+  },
+  "include": ["src", "vitest.config.ts"],
+  "exclude": ["node_modules", "dist"]
+}