feat(logger): WithSource/Scoped 日志来源标注；AGENTS 追加日志标来源+客户端API契约红线

internal/logger/logger.go

@@ -68,3 +68,24 @@ func ParseLevel(s string) slog.Level {
 		return slog.LevelInfo
 	}
 }
+
+// WithSource returns a child logger that tags every emitted record with a
+// source so issues can be traced back to the owning module/sub-feature. source
+// is conventionally "module/subfeature", e.g. "runtime/loop" or
+// "channel/adapter". Every module that logs should call this once on its base
+// logger so all records carry provenance.
+func WithSource(l *slog.Logger, source string) *slog.Logger {
+	if l == nil {
+		return nil
+	}
+	return l.With(slog.String("source", source))
+}
+
+// Scoped returns a child logger tagged with module and subfeature, for finer
+// provenance when a module contains several subsystems.
+func Scoped(l *slog.Logger, module, subfeature string) *slog.Logger {
+	if l == nil {
+		return nil
+	}
+	return l.With(slog.String("module", module), slog.String("sub", subfeature))
+}