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, 22 insertions, 22 deletions

diff --git a/src/zentelemetry/otlpencoder.cpp b/src/zentelemetry/otlpencoder.cpp
index 677545066..5477c5381 100644
--- a/src/zentelemetry/otlpencoder.cpp
+++ b/src/zentelemetry/otlpencoder.cpp
@@ -3,9 +3,9 @@
 #include "zentelemetry/otlpencoder.h"
 
 #include <zenbase/zenbase.h>
+#include <zencore/logging/logmsg.h>
 #include <zentelemetry/otlptrace.h>
 
-#include <spdlog/sinks/sink.h>
 #include <zencore/testing.h>
 
 #include <protozero/buffer_string.hpp>
@@ -29,49 +29,49 @@ OtlpEncoder::~OtlpEncoder()
 }
 
 static int
-MapSeverity(const spdlog::level::level_enum Level)
+MapSeverity(const logging::LogLevel Level)
 {
 	switch (Level)
 	{
-		case spdlog::level::critical:
+		case logging::Critical:
 			return otel::SEVERITY_NUMBER_FATAL;
-		case spdlog::level::err:
+		case logging::Err:
 			return otel::SEVERITY_NUMBER_ERROR;
-		case spdlog::level::warn:
+		case logging::Warn:
 			return otel::SEVERITY_NUMBER_WARN;
-		case spdlog::level::info:
+		case logging::Info:
 			return otel::SEVERITY_NUMBER_INFO;
-		case spdlog::level::debug:
+		case logging::Debug:
 			return otel::SEVERITY_NUMBER_DEBUG;
 		default:
-		case spdlog::level::trace:
+		case logging::Trace:
 			return otel::SEVERITY_NUMBER_TRACE;
 	}
 }
 
 static const char*
-MapSeverityText(const spdlog::level::level_enum Level)
+MapSeverityText(const logging::LogLevel Level)
 {
 	switch (Level)
 	{
-		case spdlog::level::critical:
+		case logging::Critical:
 			return "fatal";
-		case spdlog::level::err:
+		case logging::Err:
 			return "error";
-		case spdlog::level::warn:
+		case logging::Warn:
 			return "warn";
-		case spdlog::level::info:
+		case logging::Info:
 			return "info";
-		case spdlog::level::debug:
+		case logging::Debug:
 			return "debug";
 		default:
-		case spdlog::level::trace:
+		case logging::Trace:
 			return "trace";
 	}
 }
 
 std::string
-OtlpEncoder::FormatOtelProtobuf(const spdlog::details::log_msg& Msg) const
+OtlpEncoder::FormatOtelProtobuf(const logging::LogMessage& Msg) const
 {
 	std::string Data;
 
@@ -98,7 +98,7 @@ OtlpEncoder::FormatOtelProtobuf(const spdlog::details::log_msg& Msg) const
 					protozero::pbf_builder<otel::InstrumentationScope> IsBuilder{SlBuilder,
 																				 otel::ScopeLogs::required_InstrumentationScope_scope};
 
-					IsBuilder.add_string(otel::InstrumentationScope::string_name, Msg.logger_name.data(), Msg.logger_name.size());
+					IsBuilder.add_string(otel::InstrumentationScope::string_name, Msg.GetLoggerName().data(), Msg.GetLoggerName().size());
 				}
 
 				// LogRecord log_records
@@ -106,13 +106,13 @@ OtlpEncoder::FormatOtelProtobuf(const spdlog::details::log_msg& Msg) const
 					protozero::pbf_builder<otel::LogRecord> LrBuilder{SlBuilder, otel::ScopeLogs::required_repeated_LogRecord_log_records};
 
 					LrBuilder.add_fixed64(otel::LogRecord::required_fixed64_time_unix_nano,
-										  std::chrono::duration_cast<std::chrono::nanoseconds>(Msg.time.time_since_epoch()).count());
+										  std::chrono::duration_cast<std::chrono::nanoseconds>(Msg.GetTime().time_since_epoch()).count());
 
-					const int Severity = MapSeverity(Msg.level);
+					const int Severity = MapSeverity(Msg.GetLevel());
 
 					LrBuilder.add_enum(otel::LogRecord::optional_SeverityNumber_severity_number, Severity);
 
-					LrBuilder.add_string(otel::LogRecord::optional_string_severity_text, MapSeverityText(Msg.level));
+					LrBuilder.add_string(otel::LogRecord::optional_string_severity_text, MapSeverityText(Msg.GetLevel()));
 
 					otel::TraceId	   TraceId;
 					const otel::SpanId SpanId = otel::Span::GetCurrentSpanId(TraceId);
@@ -127,7 +127,7 @@ OtlpEncoder::FormatOtelProtobuf(const spdlog::details::log_msg& Msg) const
 					{
 						protozero::pbf_builder<otel::AnyValue> BodyBuilder{LrBuilder, otel::LogRecord::optional_anyvalue_body};
 
-						BodyBuilder.add_string(otel::AnyValue::string_string_value, Msg.payload.data(), Msg.payload.size());
+						BodyBuilder.add_string(otel::AnyValue::string_string_value, Msg.GetPayload().data(), Msg.GetPayload().size());
 					}
 
 					// attributes
@@ -139,7 +139,7 @@ OtlpEncoder::FormatOtelProtobuf(const spdlog::details::log_msg& Msg) const
 						{
 							protozero::pbf_builder<otel::AnyValue> AvBuilder{KvBuilder, otel::KeyValue::AnyValue_value};
 
-							AvBuilder.add_int64(otel::AnyValue::int64_int_value, Msg.thread_id);
+							AvBuilder.add_int64(otel::AnyValue::int64_int_value, Msg.GetThreadId());
 						}
 					}
 				}