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.

1 files changed, 6 insertions, 1 deletions

diff --git a/src/zen/cmds/ui_cmd.cpp b/src/zen/cmds/ui_cmd.cpp
index da06ce305..4846b4d18 100644
--- a/src/zen/cmds/ui_cmd.cpp
+++ b/src/zen/cmds/ui_cmd.cpp
@@ -50,7 +50,7 @@ UiCommand::UiCommand()
 {
 	m_Options.add_options()("h,help", "Print help");
 	m_Options.add_options()("a,all", "Open dashboard for all running instances", cxxopts::value(m_All)->default_value("false"));
-	m_Options.add_option("", "u", "hosturl", "Host URL", cxxopts::value(m_HostName)->default_value(""), "<hosturl>");
+	m_Options.add_option("", "u", "hosturl", kHostUrlHelp, cxxopts::value(m_HostName)->default_value(""), "<hosturl>");
 	m_Options.add_option("",
 						 "p",
 						 "path",
@@ -230,6 +230,11 @@ UiCommand::Run(const ZenCliOptions& GlobalOptions, int argc, char** argv)
 		throw OptionParseException("Unable to resolve server specification", m_Options.help());
 	}
 
+	if (IsUnixSocketSpec(m_HostName))
+	{
+		throw std::runtime_error("Cannot open browser for a Unix domain socket connection");
+	}
+
 	OpenBrowser(m_HostName);
 }