Redirect toolhive slog singleton to log file

Toolhive's pkg/logger maintains its own slog singleton (set during
init()) that writes JSON to stderr. The existing initToolhiveLogger
only redirected the zap global logger, so all vmcp diagnostics
(aggregator, discovery, server) still polluted the terminal session.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: JAORMX

internal/infra/mcp/provider.go

@@ -15,8 +15,10 @@ import (
 	"go.uber.org/zap/zapcore"
 
 	"github.com/stacklok/toolhive-core/env"
+	"github.com/stacklok/toolhive-core/logging"
 	thvauth "github.com/stacklok/toolhive/pkg/auth"
 	"github.com/stacklok/toolhive/pkg/groups"
+	thvlogger "github.com/stacklok/toolhive/pkg/logger"
 	"github.com/stacklok/toolhive/pkg/vmcp"
 	"github.com/stacklok/toolhive/pkg/vmcp/aggregator"
 	vmcpauthfactory "github.com/stacklok/toolhive/pkg/vmcp/auth/factory"
@@ -205,16 +207,23 @@ func (r *statusRecorder) WriteHeader(code int) {
 	r.ResponseWriter.WriteHeader(code)
 }
 
-// initToolhiveLogger configures the zap global logger used by toolhive
-// internals to write to the given writer (typically the log file).
-// If w is nil a no-op logger is installed.
+// initToolhiveLogger redirects both the zap global logger and the toolhive
+// slog singleton to the given writer (typically the apiary log file) so that
+// vmcp diagnostics don't pollute stdout/stderr during the terminal session.
+// If w is nil, no-op loggers are installed for both.
 func initToolhiveLogger(w io.Writer) {
 	if w == nil {
 		zap.ReplaceGlobals(zap.NewNop())
+		thvlogger.Set(slog.New(slog.NewJSONHandler(io.Discard, nil)))
 		return
 	}
 
+	// Redirect zap (legacy toolhive code paths).
 	enc := zapcore.NewJSONEncoder(zap.NewProductionEncoderConfig())
 	core := zapcore.NewCore(enc, zapcore.AddSync(w), zap.DebugLevel)
 	zap.ReplaceGlobals(zap.New(core))
+
+	// Redirect the toolhive slog singleton — this is the primary logger used
+	// by vmcp internals (aggregator, discovery, server, etc.).
+	thvlogger.Set(logging.New(logging.WithOutput(w)))
 }