feat: Atomic update mcp image

cmd/mcp/Dockerfile

@@ -10,6 +10,8 @@ ARG COMMIT_HASH=unknown
 RUN CGO_ENABLED=0 GOOS=linux GOARCH=${TARGETARCH:-amd64} \
     go build -trimpath -ldflags "-s -w -X github.com/memohai/memoh/internal/version.CommitHash=${COMMIT_HASH}" -o /out/mcp ./cmd/mcp
 
-FROM busybox:latest
-COPY --from=build /out/mcp /mcp
-ENTRYPOINT ["/mcp"]
+FROM alpine:latest
+RUN apk add --no-cache grep
+WORKDIR /app
+COPY --from=build /out/mcp /app/mcp
+ENTRYPOINT ["/app/mcp"]

cmd/mcp/main.go

@@ -2,8 +2,12 @@ package main
 
 import (
 	"context"
+	"errors"
+	"io"
 	"log/slog"
 	"os"
+	"os/signal"
+	"syscall"
 
 	"github.com/memohai/memoh/internal/logger"
 	"github.com/memohai/memoh/internal/mcp"
@@ -12,13 +16,28 @@ import (
 )
 
 func main() {
+	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
+	defer stop()
+
 	server := gomcp.NewServer(
 		&gomcp.Implementation{Name: "memoh-mcp", Version: version.GetInfo()},
 		nil,
 	)
 	mcp.RegisterTools(server)
-	if err := server.Run(context.Background(), &gomcp.StdioTransport{}); err != nil {
-		logger.Error("mcp server failed", slog.Any("error", err))
-		os.Exit(1)
+	err := server.Run(ctx, &gomcp.StdioTransport{})
+	if ctx.Err() != nil {
+		return
 	}
+	if err == nil {
+		logger.Warn("mcp server exited without error; waiting for shutdown signal")
+		<-ctx.Done()
+		return
+	}
+	if errors.Is(err, io.EOF) {
+		logger.Warn("mcp stdio closed; waiting for shutdown signal")
+		<-ctx.Done()
+		return
+	}
+	logger.Error("mcp server failed", slog.Any("error", err))
+	os.Exit(1)
 }