Improve comments for remainingBodyLength() to cover all states

Co-authored-by: uNetworkingAB <110806833+uNetworkingAB@users.noreply.github.com>

Author: Copilot

src/HttpParser.h

@@ -615,7 +615,7 @@ struct HttpParser {
     }
 
 public:
-    /* Returns the remaining body length if set via content-length, or UINT64_MAX if transfer-encoding is chunked */
+    /* Returns the remaining body length if set via content-length, UINT64_MAX if transfer-encoding is chunked, or 0 if no body */
     uint64_t remainingBodyLength() {
         if (isParsingChunkedEncoding(remainingStreamingBytes)) {
             return UINT64_MAX;

src/HttpResponse.h

@@ -488,7 +488,7 @@ struct HttpResponse : public AsyncSocket<SSL> {
         return httpResponseData->offset;
     }
 
-    /* Get the remaining body length, or UINT64_MAX if transfer-encoding is chunked */
+    /* Get the remaining body length if set via content-length, UINT64_MAX if transfer-encoding is chunked, or 0 if no body */
     uint64_t remainingBodyLength() {
         HttpResponseData<SSL> *httpResponseData = getHttpResponseData();