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, 3 insertions, 3 deletions

diff --git a/src/zenserver/hub/hydration.cpp b/src/zenserver/hub/hydration.cpp
index 4a44da052..541127590 100644
--- a/src/zenserver/hub/hydration.cpp
+++ b/src/zenserver/hub/hydration.cpp
@@ -916,9 +916,9 @@ TEST_CASE("hydration.s3.current_state_json_selects_latest_folder")
 		Hydrator->Dehydrate();
 	}
 
-	// ServerStateDir is now empty. Wait briefly so the v2 timestamp folder name is strictly later
-	// (timestamp resolution is 1 ms).
-	Sleep(2);
+	// ServerStateDir is now empty. Wait so the v2 timestamp folder name is strictly later
+	// (timestamp resolution is 1 ms, but macOS scheduler granularity requires a larger margin).
+	Sleep(100);
 
 	// v2: dehydrate WITH a marker file that only v2 has
 	CreateTestTree(ServerStateDir);