Stage 3: Frame the Response

Clients don't read your intentions — they read bytes. A malformed status line or a wrong Content-Length and curl hangs forever waiting for bytes you never promised correctly. Framing is the contract.

Implement buildResponse(status, headers, body) returning the raw HTTP/1.1 response string:

• status line HTTP/1.1 <code> <reason> — know at least 200 OK, 201 Created, 204 No Content, 301 Moved Permanently, 400 Bad Request, 404 Not Found, 405 Method Not Allowed, 500 Internal Server Error
• your headers, each Name: value\r\n, in the order given
• a correct Content-Length header (byte length of the body — measure, don't assume; multi-byte characters exist) appended after the given headers
• blank line, then the body. A 204 has no body and no Content-Length.