Logger simplification (#883)

- **`Logger` now holds a single `SinkPtr`** instead of a `std::vector<SinkPtr>`. The `SetSinks`/`AddSink` API is replaced with a single `SetSink`. This removes complexity from `Logger` itself and makes `Clone()` cheaper (no vector copy).

- **New `BroadcastSink`** (`zencore/logging/broadcastsink.h`) acts as a thread-safe, shared indirection point that fans out to a dynamic list of child sinks. Adding or removing a child sink via `AddSink`/`RemoveSink` is immediately visible to every `Logger` that holds a reference to it — including cloned loggers — without requiring each logger to be updated individually.

- **`GetDefaultBroadcastSink()`** (exposed from `zenutil/logging.h`) gives server-layer code access to the shared broadcast sink so it can register optional sinks (OTel, TCP log stream) after logging is initialized, without going through `Default()->AddSink()`.

### Motivation

Previously, dynamically adding sinks post-initialization mutated the default logger's internal sink vector directly. This was fragile: cloned loggers (created before `AddSink` was called) would not pick up the new sinks. `BroadcastSink` fixes this by making the sink list a shared, mutable object that all loggers sharing the same broadcast instance observe uniformly.

1 files changed, 2 insertions, 2 deletions

diff --git a/src/zencore/logging.cpp b/src/zencore/logging.cpp
index 3206e380b..828bea6ed 100644
--- a/src/zencore/logging.cpp
+++ b/src/zencore/logging.cpp
@@ -345,7 +345,7 @@ SuppressConsoleLog()
 	}
 
 	SinkPtr NullSinkPtr(new NullSink());
-	ConLogger = Ref<Logger>(new Logger("console", std::vector<SinkPtr>{NullSinkPtr}));
+	ConLogger = Ref<Logger>(new Logger("console", NullSinkPtr));
 	Registry::Instance().Register(ConLogger);
 }
 
@@ -391,7 +391,7 @@ ConsoleLog()
 		{
 			SinkPtr ConsoleSink(new AnsiColorStdoutSink());
 			ConsoleSink->SetFormatter(std::make_unique<ConsoleFormatter>());
-			ConLogger = Ref<Logger>(new Logger("console", std::vector<SinkPtr>{ConsoleSink}));
+			ConLogger = Ref<Logger>(new Logger("console", ConsoleSink));
 			Registry::Instance().Register(ConLogger);
 		}
 	});