Install and configure Jest test runner (WCTAS-4)

Adds jest, ts-jest, ts-node, and @types/jest as devDependencies and creates
jest.config.ts with the ts-jest preset. `npm test` exits 0 with no test files.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

CLAUDE.md

@@ -2,7 +2,7 @@
 
 ## Project Status
 
-Node.js/TypeScript project initialized with npm and tsconfig. Source code implementation is pending.
+Node.js/TypeScript project initialized with npm, tsconfig, and Jest (ts-jest). Source code implementation is pending.
 
 ## Build Commands
 
@@ -33,6 +33,7 @@ word-counter-api/
 ├── src/              # TypeScript source files (to be added)
 │   └── server.ts     # Entry point
 ├── dist/             # Compiled JavaScript output (gitignored)
+├── jest.config.ts    # Jest config (ts-jest preset, passWithNoTests)
 ├── package.json      # npm manifest with build/start/dev/test scripts
 ├── tsconfig.json     # TypeScript config (CommonJS, strict mode)
 ├── .gitignore

jest.config.ts

@@ -0,0 +1,9 @@
+import type { Config } from 'jest';
+
+const config: Config = {
+  preset: 'ts-jest',
+  testEnvironment: 'node',
+  passWithNoTests: true,
+};
+
+export default config;

package.json

@@ -17,7 +17,11 @@
   },
   "devDependencies": {
     "@types/express": "^4.17.0",
+    "@types/jest": "^29.5.14",
     "@types/node": "^22.0.0",
+    "jest": "^29.7.0",
+    "ts-jest": "^29.4.11",
+    "ts-node": "^10.9.2",
     "tsx": "^4.0.0",
     "typescript": "^5.0.0"
   }