Unix Domain Socket auto discovery (#833)

This PR adds end-to-end Unix domain socket (UDS) support, allowing zen CLI to discover and connect to UDS-only servers automatically.

- **`unix://` URI scheme in zen CLI**: The `-u` / `--hosturl` option now accepts `unix:///path/to/socket` to connect to a zenserver via a Unix domain socket instead of TCP.
- **Per-instance shared memory for extended server info**: Each zenserver instance now publishes a small shared memory section (keyed by SessionId) containing per-instance data that doesn't fit in the fixed-size ZenServerEntry -- starting with the UDS socket path. This is a 4KB pagefile-backed section on Windows (`Global\ZenInstance_{sessionid}`) and a POSIX shared memory object on Linux/Mac (`/UnrealEngineZen_{sessionid}`).
- **Client-side auto-discovery of UDS servers**: `zen info`, `zen status`, etc. now automatically discover and prefer UDS connections when a server publishes a socket path. Servers running with `--no-network` (UDS-only) are no longer invisible to the CLI.
- **`kNoNetwork` flag in ZenServerEntry**: Servers started with `--no-network` advertise this in their shared state entry. Clients skip TCP fallback for these servers, and display commands (`ps`, `status`, `top`) show `-` instead of a port number to indicate TCP is not available.

7 files changed, 22 insertions, 10 deletions

diff --git a/src/zenhttp/clients/httpclientcpr.cpp b/src/zenhttp/clients/httpclientcpr.cpp
index a0f5cc38f..a52b8f74b 100644
--- a/src/zenhttp/clients/httpclientcpr.cpp
+++ b/src/zenhttp/clients/httpclientcpr.cpp
@@ -7,6 +7,7 @@
 #include <zencore/compactbinarypackage.h>
 #include <zencore/compactbinaryutil.h>
 #include <zencore/compress.h>
+#include <zencore/filesystem.h>
 #include <zencore/iobuffer.h>
 #include <zencore/iohash.h>
 #include <zencore/session.h>
@@ -513,7 +514,7 @@ CprHttpClient::AllocSession(const std::string_view				 BaseUrl,
 
 	if (!ConnectionSettings.UnixSocketPath.empty())
 	{
-		CprSession->SetUnixSocket(cpr::UnixSocket(ConnectionSettings.UnixSocketPath));
+		CprSession->SetUnixSocket(cpr::UnixSocket(PathToUtf8(ConnectionSettings.UnixSocketPath)));
 	}
 
 	if (ConnectionSettings.InsecureSsl || !ConnectionSettings.CaBundlePath.empty())
diff --git a/src/zenhttp/clients/httpclientcurl.cpp b/src/zenhttp/clients/httpclientcurl.cpp
index 0dbd5b975..ec9b7bac6 100644
--- a/src/zenhttp/clients/httpclientcurl.cpp
+++ b/src/zenhttp/clients/httpclientcurl.cpp
@@ -8,6 +8,7 @@
 #include <zencore/compactbinaryutil.h>
 #include <zencore/compress.h>
 #include <zencore/except.h>
+#include <zencore/filesystem.h>
 #include <zencore/iobuffer.h>
 #include <zencore/iohash.h>
 #include <zencore/session.h>
@@ -808,7 +809,8 @@ CurlHttpClient::AllocSession(std::string_view ResourcePath, const KeyValueMap& P
 	// Unix domain socket
 	if (!m_ConnectionSettings.UnixSocketPath.empty())
 	{
-		curl_easy_setopt(Handle, CURLOPT_UNIX_SOCKET_PATH, m_ConnectionSettings.UnixSocketPath.c_str());
+		std::string SocketPathUtf8 = PathToUtf8(m_ConnectionSettings.UnixSocketPath);
+		curl_easy_setopt(Handle, CURLOPT_UNIX_SOCKET_PATH, SocketPathUtf8.c_str());
 	}
 
 	// Build URL with parameters
diff --git a/src/zenhttp/clients/httpwsclient.cpp b/src/zenhttp/clients/httpwsclient.cpp
index 2d566ae86..fbae9f5fe 100644
--- a/src/zenhttp/clients/httpwsclient.cpp
+++ b/src/zenhttp/clients/httpwsclient.cpp
@@ -5,6 +5,8 @@
 #include "../servers/wsframecodec.h"
 
 #include <zencore/base64.h>
+#include <zencore/filesystem.h>
+#include <zencore/fmtutils.h>
 #include <zencore/logging.h>
 #include <zencore/string.h>
 
@@ -155,7 +157,7 @@ struct HttpWsClient::Impl
 			}
 		});
 
-		asio::local::stream_protocol::endpoint Endpoint(m_Settings.UnixSocketPath);
+		asio::local::stream_protocol::endpoint Endpoint(PathToUtf8(m_Settings.UnixSocketPath));
 		m_UnixSocket->async_connect(Endpoint, [this](const asio::error_code& Ec) {
 			if (Ec)
 			{
diff --git a/src/zenhttp/httpserver.cpp b/src/zenhttp/httpserver.cpp
index 6ba0ca563..672467f56 100644
--- a/src/zenhttp/httpserver.cpp
+++ b/src/zenhttp/httpserver.cpp
@@ -2,6 +2,8 @@
 
 #include <zenhttp/httpserver.h>
 
+#include <zencore/filesystem.h>
+
 #include "servers/httpasio.h"
 #include "servers/httpmulti.h"
 #include "servers/httpnull.h"
@@ -1157,7 +1159,7 @@ CreateHttpServerClass(const std::string_view ServerClass, const HttpServerConfig
 		ZEN_INFO("using asio HTTP server implementation")
 		return CreateHttpAsioServer(AsioConfig {
 			.ThreadCount = Config.ThreadCount, .ForceLoopback = Config.ForceLoopback, .IsDedicatedServer = Config.IsDedicatedServer,
-			.NoNetwork = Config.NoNetwork, .UnixSocketPath = Config.UnixSocketPath,
+			.NoNetwork = Config.NoNetwork, .UnixSocketPath = PathToUtf8(Config.UnixSocketPath),
 #if ZEN_USE_OPENSSL
 			.HttpsPort = Config.HttpsPort, .CertFile = Config.CertFile, .KeyFile = Config.KeyFile,
 #endif
diff --git a/src/zenhttp/include/zenhttp/httpclient.h b/src/zenhttp/include/zenhttp/httpclient.h
index 03c98af7e..e95d78772 100644
--- a/src/zenhttp/include/zenhttp/httpclient.h
+++ b/src/zenhttp/include/zenhttp/httpclient.h
@@ -10,6 +10,7 @@
 #include <zencore/uid.h>
 #include <zenhttp/httpcommon.h>
 
+#include <filesystem>
 #include <functional>
 #include <optional>
 #include <unordered_map>
@@ -91,7 +92,7 @@ struct HttpClientSettings
 
 	/// Unix domain socket path. When non-empty, the client connects via this
 	/// socket instead of TCP. BaseUri is still used for the Host header and URL.
-	std::string UnixSocketPath;
+	std::filesystem::path UnixSocketPath;
 
 	/// Disable HTTP keep-alive by closing the connection after each request.
 	/// Useful for testing per-connection overhead.
@@ -174,11 +175,14 @@ class HttpClientBase;
 class HttpClient
 {
 public:
-	HttpClient(std::string_view			 BaseUri,
-			   const HttpClientSettings& Connectionsettings	  = {},
-			   std::function<bool()>&&	 CheckIfAbortFunction = {});
+	explicit HttpClient(std::string_view		  BaseUri,
+						const HttpClientSettings& Connectionsettings   = {},
+						std::function<bool()>&&	  CheckIfAbortFunction = {});
 	~HttpClient();
 
+	HttpClient(const HttpClient&) = delete;
+	HttpClient& operator=(const HttpClient&) = delete;
+
 	struct ErrorContext
 	{
 		HttpClientErrorCode ErrorCode;
diff --git a/src/zenhttp/include/zenhttp/httpserver.h b/src/zenhttp/include/zenhttp/httpserver.h
index 627e7921f..77feb6568 100644
--- a/src/zenhttp/include/zenhttp/httpserver.h
+++ b/src/zenhttp/include/zenhttp/httpserver.h
@@ -15,6 +15,7 @@
 
 #include <zentelemetry/stats.h>
 
+#include <filesystem>
 #include <functional>
 #include <gsl/gsl-lite.hpp>
 #include <list>
@@ -329,7 +330,7 @@ struct HttpServerConfig
 	std::vector<HttpServerPluginConfig> PluginConfigs;
 	bool								ForceLoopback = false;
 	unsigned int						ThreadCount	  = 0;
-	std::string							UnixSocketPath;		// Unix domain socket path (empty = disabled, non-Windows only)
+	std::filesystem::path				UnixSocketPath;		// Unix domain socket path (empty = disabled)
 	bool								NoNetwork = false;	// Disable TCP/HTTPS listeners; only accept connections via UnixSocketPath
 	int									HttpsPort = 0;		// HTTPS listen port (0 = disabled, ASIO backend)
 	std::string							CertFile;			// PEM certificate chain file path
diff --git a/src/zenhttp/include/zenhttp/httpwsclient.h b/src/zenhttp/include/zenhttp/httpwsclient.h
index 34d338b1d..2ca9b7ab1 100644
--- a/src/zenhttp/include/zenhttp/httpwsclient.h
+++ b/src/zenhttp/include/zenhttp/httpwsclient.h
@@ -46,7 +46,7 @@ struct HttpWsClientSettings
 
 	/// Unix domain socket path. When non-empty, connects via this socket
 	/// instead of TCP. The URL host is still used for the Host header.
-	std::string UnixSocketPath;
+	std::filesystem::path UnixSocketPath;
 };
 
 /**