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, 2 insertions, 0 deletions

diff --git a/src/zenserver/zenserver.cpp b/src/zenserver/zenserver.cpp
index de770156a..6aa02eb87 100644
--- a/src/zenserver/zenserver.cpp
+++ b/src/zenserver/zenserver.cpp
@@ -489,6 +489,7 @@ ZenServerBase::BuildSettingsList(const ZenServerConfig& ServerConfig)
 		{"BasePort"sv, 				fmt::to_string(ServerConfig.BasePort)},
 		{"CoreLimit"sv, 			fmt::to_string(ServerConfig.CoreLimit)},
 		{"MemoryAllocator"sv,		std::string(GMalloc->GetName())},
+		{"AsioVersion"sv,			fmt::format("{}.{}.{}", ASIO_VERSION / 100000, (ASIO_VERSION / 100) % 1000, ASIO_VERSION % 100)},
 		{"IsDebug"sv, 				fmt::to_string(ServerConfig.IsDebug)},
 		{"IsCleanStart"sv, 			fmt::to_string(ServerConfig.IsCleanStart)},
 		{"IsTest"sv, 				fmt::to_string(ServerConfig.IsTest)},
@@ -771,6 +772,7 @@ ZenServerMain::Run()
 
 		ZEN_INFO(ZEN_APP_NAME " - starting on port {}, version '{}'", m_ServerOptions.BasePort, ZEN_CFG_VERSION_BUILD_STRING_FULL);
 		ZEN_INFO(ZEN_APP_NAME " - memory allocator: {}", GMalloc->GetName());
+		ZEN_INFO(ZEN_APP_NAME " - asio: {}.{}.{}", ASIO_VERSION / 100000, (ASIO_VERSION / 100) % 1000, ASIO_VERSION % 100);
 
 		Entry = ServerState.Register(m_ServerOptions.BasePort);