[Fix] (MG_Remote): the socket-io stats are LinkMetrics free functions, not StreamLink members

6bccf98d7 put TakeSendStats/TakeReadStats on the concrete StreamLink class, so
ClientSession.cpp and ServerLoop.cpp had to include <MG_Remote/Transport/StreamLink.h> -
which the P6.5 seam gate (scripts/ci/link_seam_purity.py, "concrete link included above
Transport") rejects, and the MGPipe generators and hygiene gates job has been red since.

The counters stay in StreamLink.cpp beside the recv/sendmsg loops that feed them; only the
struct and the two Take functions move, to LinkMetrics.h as LinkIoStats +
LinkMetricsTakeReadStats/TakeSendStats. The readers drop the concrete include; the hot
loops are untouched.

MobileGL/MG_Remote/Client/ClientSession.cpp

@@ -13,7 +13,6 @@
 #include <MG_Remote/FatalFunnel.h>
 #include <MG_Remote/Handshake.h>
 #include <MG_Remote/Transport/LinkMetrics.h>
-#include <MG_Remote/Transport/StreamLink.h>
 
 #include "../CapsCodec.h"
 #include "../Protocol/generated/protocol_generated.h"
@@ -2300,7 +2299,7 @@ namespace MobileGL::MG_Remote::Client {
             const double creditMs =
                 static_cast<double>(std::chrono::duration_cast<std::chrono::nanoseconds>(
                     std::chrono::steady_clock::now() - paceStarted).count()) / 1e6;
-            const auto io = Transport::StreamLink::TakeSendStats();
+            const auto io = Transport::LinkMetricsTakeSendStats();
             MGLOG_I("P65ClientPace present=%llu credit_wait_ms=%.1f | io: %llu B in %llu sendmsg "
                     "send_ms=%.1f total_ms=%.1f",
                     static_cast<unsigned long long>(serial), creditMs,