**test(api): add integration tests for API endpoints and core functionality**

- **Integration Tests**:
  - Introduced `api-integration.test.ts` to validate API functionality:
    - Verifies text insertion, vector embedding generation, and search operations.
    - Confirms HNSW index correctness for vector similarity search.
    - Ensures no dimensional mismatches in embeddings.

- **Test Server**:
  - Added test server utilizing Express for endpoint simulation (`/insert` and `/search/text`).

- **Dependencies**:
  - Introduced `express` and `node-fetch` as new dependencies for testing purposes.

- **Vitest Fix**:
  - Updated `vitest.config.ts` to resolve the `process.memoryUsage` error by setting `logHeapUsage: false`.

- **Package Updates**:
  - Modified `package-lock.json` to include newly added dependencies and updates.

**Purpose**: Guarantees the stability of core API endpoints and vector-related functionality, ensuring reliable behavior for end-to-end scenarios.

fix-documentation.md

@@ -0,0 +1,34 @@
+# Fix for "process.memoryUsage is not a function" Error
+
+## Issue
+During test runs with Vitest, the following error was occurring:
+
+```
+TypeError: process.memoryUsage is not a function
+ ❯ VitestTestRunner.onAfterRunSuite node_modules/vitest/dist/runners.js:150:95
+```
+
+This error was happening because Vitest was trying to use `process.memoryUsage()` to log heap usage statistics, but this function was not available in the current environment.
+
+## Solution
+The issue was fixed by disabling the heap usage logging in the Vitest configuration:
+
+In `vitest.config.ts`, changed:
+```typescript
+// Show test statistics
+logHeapUsage: true,
+```
+
+To:
+```typescript
+// Show test statistics
+logHeapUsage: false,
+```
+
+## Explanation
+The `logHeapUsage` option in Vitest attempts to use Node.js's `process.memoryUsage()` function to track and report memory usage during test runs. However, this function might not be available in all environments, particularly in certain browser-like environments or when using specific Node.js versions or configurations.
+
+By setting `logHeapUsage: false`, we prevent Vitest from attempting to call this function, which resolves the error while still allowing tests to run successfully.
+
+## Verification
+After making this change, the tests run without any unhandled errors, confirming that the issue has been resolved.