fix: suppress response body for HEAD requests

HEAD responses must have identical headers to GET but no body (RFC 9110 §9.3.2).
uWS is low-level and doesn't strip bodies for HEAD automatically.

- In endResponse(), check req.method === 'HEAD' and use endWithoutBody()
  or end() without body when method is HEAD
- Add unit tests for HEAD request handling

Fixes #151

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: qianmao1989

src/http/core/response.spec.ts

@@ -565,6 +565,41 @@ describe('UwsResponse', () => {
     });
   });
 
+  describe('HEAD request handling', () => {
+    it('should suppress body for HEAD request with content-length', () => {
+      res = createResponse();
+      const mockReq = { method: 'HEAD' } as any;
+      res.bindRequest(mockReq);
+
+      res.setHeader('content-length', '1024').send('Hello');
+
+      expect(mockUwsRes.endWithoutBody).toHaveBeenCalledWith(1024);
+      expect(mockUwsRes.end).not.toHaveBeenCalled();
+    });
+
+    it('should suppress body for HEAD request without content-length', () => {
+      res = createResponse();
+      const mockReq = { method: 'HEAD' } as any;
+      res.bindRequest(mockReq);
+
+      res.send('Hello');
+
+      expect(mockUwsRes.end).toHaveBeenCalledWith();
+      expect(mockUwsRes.endWithoutBody).not.toHaveBeenCalled();
+    });
+
+    it('should send body normally for GET request', () => {
+      res = createResponse();
+      const mockReq = { method: 'GET' } as any;
+      res.bindRequest(mockReq);
+
+      res.send('Hello');
+
+      expect(mockUwsRes.end).toHaveBeenCalledWith('Hello');
+      expect(mockUwsRes.endWithoutBody).not.toHaveBeenCalled();
+    });
+  });
+
   describe('json()', () => {
     beforeEach(() => {
       res = createResponse();

src/http/core/response.ts

@@ -1390,6 +1390,15 @@ export class UwsResponse extends Writable {
   }
 
   private endResponse(body: string | Buffer | undefined): void {
+    // HEAD responses must have identical headers to GET but no body (RFC 9110 §9.3.2)
+    if (this.req?.method === 'HEAD') {
+      if (this.contentLengthTotal !== undefined) {
+        this.uwsRes.endWithoutBody(this.contentLengthTotal);
+      } else {
+        this.uwsRes.end();
+      }
+      return;
+    }
     if (body !== undefined) {
       this.uwsRes.end(body);
       return;