Eliminate spdlog dependency (#773)

Removes the vendored spdlog library (~12,000 lines) and replaces it with a purpose-built logging system in zencore (~1,800 lines). The new implementation provides the same functionality with fewer abstractions, no shared_ptr overhead, and full control over the logging pipeline.

### What changed

**New logging core in zencore/logging/:**
- LogMessage, Formatter, Sink, Logger, Registry - core abstractions matching spdlog's model but simplified
- AnsiColorStdoutSink - ANSI color console output (replaces spdlog stdout_color_sink)
- MsvcSink - OutputDebugString on Windows (replaces spdlog msvc_sink)
- AsyncSink - async logging via BlockingQueue worker thread (replaces spdlog async_logger)
- NullSink, MessageOnlyFormatter - utility types
- Thread-safe timestamp caching in formatters using RwLock

**Moved to zenutil/logging/:**
- FullFormatter - full log formatting with timestamp, logger name, level, source location, multiline alignment
- JsonFormatter - structured JSON log output
- RotatingFileSink - rotating file sink with atomic size tracking

**API changes:**
- Log levels are now an enum (LogLevel) instead of int, eliminating the zen::logging::level namespace
- LoggerRef no longer wraps shared_ptr - it holds a raw pointer with the registry owning lifetime
- Logger error handler is wired through Registry and propagated to all loggers on registration
- Logger::Log() now populates ThreadId on every message

**Cleanup:**
- Deleted thirdparty/spdlog/ entirely (110+ files)
- Deleted full_test_formatter (was ~80% duplicate of FullFormatter)
- Renamed snake_case classes to PascalCase (full_formatter -> FullFormatter, json_formatter -> JsonFormatter, sentry_sink -> SentrySink)
- Removed spdlog from xmake dependency graph

### Build / test impact

- zencore no longer depends on spdlog
- zenutil and zenvfs xmake.lua updated to drop spdlog dep
- zentelemetry xmake.lua updated to drop spdlog dep
- All existing tests pass, no test changes required beyond formatter class renames

1 files changed, 11 insertions, 11 deletions

diff --git a/src/zenutil/config/loggingconfig.cpp b/src/zenutil/config/loggingconfig.cpp
index 9ec816b1b..5092c60aa 100644
--- a/src/zenutil/config/loggingconfig.cpp
+++ b/src/zenutil/config/loggingconfig.cpp
@@ -21,13 +21,13 @@ ZenLoggingCmdLineOptions::AddCliOptions(cxxopts::Options& options, ZenLoggingCon
 		("log-id",			"Specify id for adding context to log output",				cxxopts::value<std::string>(LoggingConfig.LogId))
 		("quiet",			"Configure console logger output to level WARN",			cxxopts::value<bool>(LoggingConfig.QuietConsole)->default_value("false"))
 		("noconsole",		"Disable console logging",									cxxopts::value<bool>(LoggingConfig.NoConsoleOutput)->default_value("false"))
-		("log-trace", 		"Change selected loggers to level TRACE", 					cxxopts::value<std::string>(LoggingConfig.Loggers[logging::level::Trace]))
-		("log-debug", 		"Change selected loggers to level DEBUG", 					cxxopts::value<std::string>(LoggingConfig.Loggers[logging::level::Debug]))
-		("log-info", 		"Change selected loggers to level INFO", 					cxxopts::value<std::string>(LoggingConfig.Loggers[logging::level::Info]))
-		("log-warn", 		"Change selected loggers to level WARN", 					cxxopts::value<std::string>(LoggingConfig.Loggers[logging::level::Warn]))
-		("log-error", 		"Change selected loggers to level ERROR", 					cxxopts::value<std::string>(LoggingConfig.Loggers[logging::level::Err]))
-		("log-critical", 	"Change selected loggers to level CRITICAL", 				cxxopts::value<std::string>(LoggingConfig.Loggers[logging::level::Critical]))
-		("log-off", 		"Change selected loggers to level OFF", 					cxxopts::value<std::string>(LoggingConfig.Loggers[logging::level::Off]))
+		("log-trace", 		"Change selected loggers to level TRACE", 					cxxopts::value<std::string>(LoggingConfig.Loggers[logging::Trace]))
+		("log-debug", 		"Change selected loggers to level DEBUG", 					cxxopts::value<std::string>(LoggingConfig.Loggers[logging::Debug]))
+		("log-info", 		"Change selected loggers to level INFO", 					cxxopts::value<std::string>(LoggingConfig.Loggers[logging::Info]))
+		("log-warn", 		"Change selected loggers to level WARN", 					cxxopts::value<std::string>(LoggingConfig.Loggers[logging::Warn]))
+		("log-error", 		"Change selected loggers to level ERROR", 					cxxopts::value<std::string>(LoggingConfig.Loggers[logging::Err]))
+		("log-critical", 	"Change selected loggers to level CRITICAL", 				cxxopts::value<std::string>(LoggingConfig.Loggers[logging::Critical]))
+		("log-off", 		"Change selected loggers to level OFF", 					cxxopts::value<std::string>(LoggingConfig.Loggers[logging::Off]))
 		("otlp-endpoint", 	"OpenTelemetry endpoint URI (e.g http://localhost:4318)", 	cxxopts::value<std::string>(LoggingConfig.OtelEndpointUri))
 	;
 	// clang-format on
@@ -47,7 +47,7 @@ ApplyLoggingOptions(cxxopts::Options& options, ZenLoggingConfig& LoggingConfig)
 	if (LoggingConfig.QuietConsole)
 	{
 		bool HasExplicitConsoleLevel = false;
-		for (int i = 0; i < logging::level::LogLevelCount; ++i)
+		for (int i = 0; i < logging::LogLevelCount; ++i)
 		{
 			if (LoggingConfig.Loggers[i].find("console") != std::string::npos)
 			{
@@ -58,7 +58,7 @@ ApplyLoggingOptions(cxxopts::Options& options, ZenLoggingConfig& LoggingConfig)
 
 		if (!HasExplicitConsoleLevel)
 		{
-			std::string& WarnLoggers = LoggingConfig.Loggers[logging::level::Warn];
+			std::string& WarnLoggers = LoggingConfig.Loggers[logging::Warn];
 			if (!WarnLoggers.empty())
 			{
 				WarnLoggers += ",";
@@ -67,9 +67,9 @@ ApplyLoggingOptions(cxxopts::Options& options, ZenLoggingConfig& LoggingConfig)
 		}
 	}
 
-	for (int i = 0; i < logging::level::LogLevelCount; ++i)
+	for (int i = 0; i < logging::LogLevelCount; ++i)
 	{
-		logging::ConfigureLogLevels(logging::level::LogLevel(i), LoggingConfig.Loggers[i]);
+		logging::ConfigureLogLevels(logging::LogLevel(i), LoggingConfig.Loggers[i]);
 	}
 	logging::RefreshLogLevels();
 }