Cross-platform process metrics support (#887)

- **Cross-platform `GetProcessMetrics`**: Implement Linux (`/proc/{pid}/stat`, `/proc/{pid}/statm`, `/proc/{pid}/status`) and macOS (`proc_pidinfo(PROC_PIDTASKINFO)`) support for CPU times and memory metrics. Fix Windows to populate the `MemoryBytes` field (was always 0). All platforms now set `MemoryBytes = WorkingSetSize`.
- **`ProcessMetricsTracker`**: Experimental utility class (`zenutil`) that periodically samples resource usage for a set of tracked child processes. Supports both a dedicated background thread and an ASIO steady_timer mode. Computes delta-based CPU usage percentage across samples, with batched sampling (8 processes per tick) to limit per-cycle overhead.
- **`ProcessHandle` documentation**: Add Doxygen comments to all public methods describing platform-specific behavior.
- **Cleanup**: Remove unused `ZEN_RUN_TESTS` macro (inlined at its single call site in `zenserver/main.cpp`), remove dead `#if 0` thread-shutdown workaround block.
- **Minor fixes**: Use `HttpClientAccessToken` constructor in hordeclient instead of setting private members directly. Log ASIO version at startup and include it in the server settings list.

1 files changed, 148 insertions, 4 deletions

diff --git a/src/zencore/process.cpp b/src/zencore/process.cpp
index 47289a37b..dcb8b2422 100644
--- a/src/zencore/process.cpp
+++ b/src/zencore/process.cpp
@@ -1839,11 +1839,137 @@ GetProcessMetrics(const ProcessHandle& Handle, ProcessMetrics& OutMetrics)
 		OutMetrics.PeakWorkingSetSize = MemCounters.PeakWorkingSetSize;
 		OutMetrics.PagefileUsage	  = MemCounters.PagefileUsage;
 		OutMetrics.PeakPagefileUsage  = MemCounters.PeakPagefileUsage;
+		OutMetrics.MemoryBytes		  = MemCounters.WorkingSetSize;
 	}
-#else
-	// TODO: implement for Linux and Mac
-	ZEN_UNUSED(Handle);
-	ZEN_UNUSED(OutMetrics);
+#elif ZEN_PLATFORM_LINUX
+
+	const pid_t Pid = static_cast<pid_t>(Handle.Pid());
+
+	// Read CPU times from /proc/{pid}/stat
+	{
+		char Path[64];
+		snprintf(Path, sizeof(Path), "/proc/%d/stat", static_cast<int>(Pid));
+
+		char Buf[256];
+		int	 Fd = open(Path, O_RDONLY);
+		if (Fd >= 0)
+		{
+			ssize_t Len = read(Fd, Buf, sizeof(Buf) - 1);
+			close(Fd);
+
+			if (Len > 0)
+			{
+				Buf[Len] = '\0';
+
+				// Skip past "pid (name) " — find last ')' to handle names containing spaces or parens
+				const char* P = strrchr(Buf, ')');
+				if (P)
+				{
+					P += 2;	 // skip ') '
+
+					// Fields after (name): 0:state 1:ppid ... 11:utime 12:stime
+					unsigned long UTime = 0;
+					unsigned long STime = 0;
+					if (sscanf(P, "%*c %*d %*d %*d %*d %*d %*u %*u %*u %*u %*u %lu %lu", &UTime, &STime) == 2)
+					{
+						static const long ClkTck = std::max(sysconf(_SC_CLK_TCK), 1L);
+						OutMetrics.KernelTimeMs	 = STime * 1000 / ClkTck;
+						OutMetrics.UserTimeMs	 = UTime * 1000 / ClkTck;
+					}
+				}
+			}
+		}
+	}
+
+	// Read memory metrics from /proc/{pid}/statm (values in pages)
+	{
+		char Path[64];
+		snprintf(Path, sizeof(Path), "/proc/%d/statm", static_cast<int>(Pid));
+
+		char Buf[128];
+		int	 Fd = open(Path, O_RDONLY);
+		if (Fd >= 0)
+		{
+			ssize_t Len = read(Fd, Buf, sizeof(Buf) - 1);
+			close(Fd);
+
+			if (Len > 0)
+			{
+				Buf[Len] = '\0';
+
+				// Fields: size resident shared text lib data dt
+				unsigned long VmSize   = 0;
+				unsigned long Resident = 0;
+				if (sscanf(Buf, "%lu %lu", &VmSize, &Resident) == 2)
+				{
+					static const long PageSize = sysconf(_SC_PAGESIZE);
+					OutMetrics.WorkingSetSize  = Resident * PageSize;
+					OutMetrics.PagefileUsage   = VmSize * PageSize;
+				}
+			}
+		}
+	}
+
+	// Read peak RSS from /proc/{pid}/status (VmHWM line)
+	{
+		char Path[64];
+		snprintf(Path, sizeof(Path), "/proc/%d/status", static_cast<int>(Pid));
+
+		char Buf[2048];
+		int	 Fd = open(Path, O_RDONLY);
+		if (Fd >= 0)
+		{
+			ssize_t Len = read(Fd, Buf, sizeof(Buf) - 1);
+			close(Fd);
+
+			if (Len > 0)
+			{
+				Buf[Len] = '\0';
+
+				const char* VmHWM = strstr(Buf, "VmHWM:");
+				if (VmHWM)
+				{
+					unsigned long PeakRssKb = 0;
+					if (sscanf(VmHWM + 6, "%lu", &PeakRssKb) == 1)
+					{
+						OutMetrics.PeakWorkingSetSize = PeakRssKb * 1024;
+					}
+				}
+
+				const char* VmPeak = strstr(Buf, "VmPeak:");
+				if (VmPeak)
+				{
+					unsigned long PeakVmKb = 0;
+					if (sscanf(VmPeak + 7, "%lu", &PeakVmKb) == 1)
+					{
+						OutMetrics.PeakPagefileUsage = PeakVmKb * 1024;
+					}
+				}
+			}
+		}
+	}
+
+	OutMetrics.MemoryBytes = OutMetrics.WorkingSetSize;
+
+#elif ZEN_PLATFORM_MAC
+
+	const pid_t Pid = static_cast<pid_t>(Handle.Pid());
+
+	struct proc_taskinfo Info;
+	if (proc_pidinfo(Pid, PROC_PIDTASKINFO, 0, &Info, sizeof(Info)) > 0)
+	{
+		// pti_total_user and pti_total_system are in nanoseconds
+		OutMetrics.UserTimeMs	= Info.pti_total_user / 1'000'000;
+		OutMetrics.KernelTimeMs = Info.pti_total_system / 1'000'000;
+
+		OutMetrics.WorkingSetSize	  = Info.pti_resident_size;
+		OutMetrics.PeakWorkingSetSize = Info.pti_resident_size;	 // macOS doesn't track peak RSS directly
+		OutMetrics.PagefileUsage	  = Info.pti_virtual_size;
+		OutMetrics.PeakPagefileUsage  = Info.pti_virtual_size;
+	}
+
+	OutMetrics.MemoryBytes = OutMetrics.WorkingSetSize;
+
 #endif
 }
 
@@ -1885,6 +2011,24 @@ TEST_CASE("FindProcess")
 	}
 }
 
+TEST_CASE("GetProcessMetrics")
+{
+	ProcessHandle Handle;
+	Handle.Initialize(GetCurrentProcessId());
+	REQUIRE(Handle.IsValid());
+
+	ProcessMetrics Metrics;
+	GetProcessMetrics(Handle, Metrics);
+
+	// The current process should have non-zero memory usage
+	CHECK(Metrics.WorkingSetSize > 0);
+	CHECK(Metrics.MemoryBytes > 0);
+	CHECK(Metrics.MemoryBytes == Metrics.WorkingSetSize);
+
+	// CPU time should be non-zero for a running test process
+	CHECK((Metrics.UserTimeMs + Metrics.KernelTimeMs) > 0);
+}
+
 TEST_CASE("BuildArgV")
 {
 	const char* Words[] = {"one", "two", "three", "four", "five"};