Interprocess pipe support (for stdout/stderr capture) (#866)

- **RAII pipe handles for child process stdout/stderr capture**: `StdoutPipeHandles` is now a proper RAII type with automatic cleanup, move semantics, and partial close support. This makes it safe to use pipes for capturing child process output without risking handle/fd leaks.

- **Optional separate stderr pipe**: `CreateProcOptions` now accepts a `StderrPipe` field so callers can capture stdout and stderr independently. When null (default), stderr shares the stdout pipe as before.

- **LogStreamListener with pluggable handler**: The TCP log stream listener accepts connections from remote processes and delivers parsed log lines through a `LogStreamHandler` interface, set dynamically via `SetHandler()`. This allows any client to receive log messages without depending on a specific console implementation.

- **TcpLogStreamSink for zen::logging**: A logging sink that forwards log messages to a `LogStreamListener` over TCP, using the native `zen::logging::Sink` infrastructure with proper thread-safe synchronization.

- **Reliable child process exit codes on Linux**: `waitpid` result handling is fixed so `ProcessHandle::GetExitCode()` returns the real exit code. `ProcessHandle::Reset()` reaps zombies directly, replacing the global `IgnoreChildSignals()` which prevented exit code collection entirely. Also fixes a TOCTOU race in `ProcessHandle::Wait()` on Linux/Mac.

- **Pipe capture test suite**: Tests covering stdout/stderr capture via pipes (both shared and separate modes), RAII cleanup, move semantics, and exit code propagation using `zentest-appstub` as the child process.

- **Service command integration tests**: Shell-based integration tests for `zen service` covering the full lifecycle (install, status, start, stop, uninstall) on all three platforms — Linux (systemd), macOS (launchd), and Windows (SCM via PowerShell).

- **Test script reorganization**: Platform-specific test scripts moved from `scripts/test_scripts/` into `scripts/test_linux/`, `test_mac/`, and `test_windows/`.

2 files changed, 23 insertions, 4 deletions

diff --git a/src/zenserver/diag/logging.cpp b/src/zenserver/diag/logging.cpp
index 178c3d3b5..38b15480a 100644
--- a/src/zenserver/diag/logging.cpp
+++ b/src/zenserver/diag/logging.cpp
@@ -13,6 +13,7 @@
 #include <zencore/string.h>
 #include <zenutil/logging.h>
 #include <zenutil/logging/rotatingfilesink.h>
+#include <zenutil/splitconsole/tcplogstreamsink.h>
 
 #include "otlphttp.h"
 
@@ -28,6 +29,7 @@ InitializeServerLogging(const ZenServerConfig& InOptions, bool WithCacheService)
 									   .IsTest			= InOptions.IsTest,
 									   .NoConsoleOutput = InOptions.LoggingConfig.NoConsoleOutput,
 									   .QuietConsole	= InOptions.LoggingConfig.QuietConsole,
+									   .ForceColor		= InOptions.LoggingConfig.ForceColor,
 									   .AbsLogFile		= InOptions.LoggingConfig.AbsLogFile,
 									   .LogId			= InOptions.LoggingConfig.LogId};
 
@@ -81,6 +83,27 @@ InitializeServerLogging(const ZenServerConfig& InOptions, bool WithCacheService)
 	}
 #endif
 
+	if (!InOptions.LoggingConfig.LogStreamEndpoint.empty())
+	{
+		std::string Endpoint = InOptions.LoggingConfig.LogStreamEndpoint;
+		std::string Host	 = "localhost";
+		uint16_t	Port	 = 0;
+
+		auto ColonPos = Endpoint.rfind(':');
+		if (ColonPos != std::string::npos)
+		{
+			Host					  = Endpoint.substr(0, ColonPos);
+			std::optional<uint16_t> P = ParseInt<uint16_t>(std::string_view(Endpoint).substr(ColonPos + 1));
+			Port					  = P.value_or(0);
+		}
+
+		if (Port > 0)
+		{
+			logging::SinkPtr StreamSink(new TcpLogStreamSink(Host, Port, "zenserver"));
+			zen::logging::Default()->AddSink(std::move(StreamSink));
+		}
+	}
+
 	FinishInitializeLogging(LogOptions);
 
 	const zen::Oid ServerSessionId = zen::GetSessionId();
diff --git a/src/zenserver/main.cpp b/src/zenserver/main.cpp
index bf328c499..dff162b1c 100644
--- a/src/zenserver/main.cpp
+++ b/src/zenserver/main.cpp
@@ -123,10 +123,6 @@ AppMain(int argc, char* argv[])
 	signal(SIGINT, utils::SignalCallbackHandler);
 	signal(SIGTERM, utils::SignalCallbackHandler);
 
-#if ZEN_PLATFORM_LINUX
-	IgnoreChildSignals();
-#endif
-
 	try
 	{
 		typename Main::Config ServerOptions;