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, 13 deletions

diff --git a/src/zenremotestore/include/zenremotestore/operationlogoutput.h b/src/zenremotestore/include/zenremotestore/operationlogoutput.h
index 6f10ab156..32b95f50f 100644
--- a/src/zenremotestore/include/zenremotestore/operationlogoutput.h
+++ b/src/zenremotestore/include/zenremotestore/operationlogoutput.h
@@ -11,7 +11,7 @@ class OperationLogOutput
 {
 public:
 	virtual ~OperationLogOutput() {}
-	virtual void EmitLogMessage(int LogLevel, std::string_view Format, fmt::format_args Args) = 0;
+	virtual void EmitLogMessage(const logging::LogPoint& Point, fmt::format_args Args) = 0;
 
 	virtual void	 SetLogOperationName(std::string_view Name)						 = 0;
 	virtual void	 SetLogOperationProgress(uint32_t StepIndex, uint32_t StepCount) = 0;
@@ -60,19 +60,17 @@ public:
 
 OperationLogOutput* CreateStandardLogOutput(LoggerRef Log);
 
-#define ZEN_OPERATION_LOG(OutputTarget, InLevel, fmtstr, ...)                                         \
-	do                                                                                                \
-	{                                                                                                 \
-		using namespace std::literals;                                                                \
-		ZEN_CHECK_FORMAT_STRING(fmtstr##sv, ##__VA_ARGS__);                                           \
-		OutputTarget.EmitLogMessage(InLevel, fmtstr, zen::logging::LogCaptureArguments(__VA_ARGS__)); \
+#define ZEN_OPERATION_LOG(OutputTarget, InLevel, fmtstr, ...)                                    \
+	do                                                                                           \
+	{                                                                                            \
+		using namespace std::literals;                                                           \
+		static constinit zen::logging::LogPoint LogPoint{{}, InLevel, std::string_view(fmtstr)}; \
+		ZEN_CHECK_FORMAT_STRING(fmtstr##sv, ##__VA_ARGS__);                                      \
+		(OutputTarget).EmitLogMessage(LogPoint, zen::logging::LogCaptureArguments(__VA_ARGS__)); \
 	} while (false)
 
-#define ZEN_OPERATION_LOG_INFO(OutputTarget, fmtstr, ...) \
-	ZEN_OPERATION_LOG((OutputTarget), zen::logging::level::Info, fmtstr, ##__VA_ARGS__)
-#define ZEN_OPERATION_LOG_DEBUG(OutputTarget, fmtstr, ...) \
-	ZEN_OPERATION_LOG((OutputTarget), zen::logging::level::Debug, fmtstr, ##__VA_ARGS__)
-#define ZEN_OPERATION_LOG_WARN(OutputTarget, fmtstr, ...) \
-	ZEN_OPERATION_LOG((OutputTarget), zen::logging::level::Warn, fmtstr, ##__VA_ARGS__)
+#define ZEN_OPERATION_LOG_INFO(OutputTarget, fmtstr, ...)  ZEN_OPERATION_LOG(OutputTarget, zen::logging::Info, fmtstr, ##__VA_ARGS__)
+#define ZEN_OPERATION_LOG_DEBUG(OutputTarget, fmtstr, ...) ZEN_OPERATION_LOG(OutputTarget, zen::logging::Debug, fmtstr, ##__VA_ARGS__)
+#define ZEN_OPERATION_LOG_WARN(OutputTarget, fmtstr, ...)  ZEN_OPERATION_LOG(OutputTarget, zen::logging::Warn, fmtstr, ##__VA_ARGS__)
 
 }  // namespace zen