Headless: Run several instances that talk to each other over ad hoc

--instance=N sets PPSSPP_ID, so each instance gets its own 127.0.0.N address
and MAC; headless left it at 0, which made its address 127.0.0.0.
--realtime keeps emulated time from running ahead of the wall clock. Only
display flips paced headless, and a test that doesn't draw never flips, so
two instances waiting for each other over the network timed out at once.
--adhoc-server runs the built-in ad hoc server.

Tools/adhoc_multi.py runs a multi-console pspautotest (X_host, X_client,
X_client2, ...) on one instance per role, with the built-in server or, with
--relay, a local aemu_postoffice in relay mode.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Core/CmdLine.cpp

@@ -254,6 +254,9 @@ static const CommandLineParam g_autoParams[] = {
 	{POFF(timeoutEmulated), CmdParamType::Double, "timeout-emulated", '\0', "Stop the run after this many emulated seconds", CmdLineMode::Headless},
 	// The old name for --timeout-wall, kept working because it's in a lot of scripts.
 	{POFF(timeoutWall), CmdParamType::Double, "timeout", '\0', "Alias for --timeout-wall", CmdLineMode::Headless},
+	{POFF(instance), CmdParamType::Int, "instance", '\0', "Run as instance N of several talking to each other over ad hoc (own 127.0.0.N address and MAC)", CmdLineMode::Headless},
+	{POFF(realtime), CmdParamType::Bool, "realtime", '\0', "Run at PSP speed instead of as fast as possible", CmdLineMode::Headless},
+	{POFF(adhocServer), CmdParamType::Bool, "adhoc-server", '\0', "Run the built-in ad hoc server"},
 	{POFF(frameStats), CmdParamType::Bool, "frame-stats", '\0', "Print flips per emulated second at the end of the run, counted from --state's load", CmdLineMode::Headless},
 	{POFF(maxScreenshotError), CmdParamType::Double, "max-mse", '\0', "Maximum allowed MSE error for screenshot comparison", CmdLineMode::Headless},
 	{POFF(mountIso), CmdParamType::String, "mount", 'm', "Mount ISO/CSO on umd1: when booting an ELF/PBP or --vsh"},
@@ -566,6 +569,10 @@ CommandLineParseResult CommandLineOptions::Parse(int argc, const char *argv[], C
 }
 
 void CommandLineOptions::ApplyToConfig() const {
+	if (adhocServer.has_value()) {
+		g_Config.bEnableAdhocServer = adhocServer.value();
+		g_Config.DoNotSaveSetting(&g_Config.bEnableAdhocServer);
+	}
 	if (fuseId.has_value()) {
 		g_Config.sFuseID = fuseId.value();
 		g_Config.DoNotSaveSetting(&g_Config.sFuseID);