Add mcp logs command for streaming container logs

New server-streaming Logs RPC streams container output to the CLI.
Supports --tail/-n, --follow/-f, --timestamps/-t, --since.

Detects journald log driver and falls back to journalctl (podman logs
can't read journald outside the originating user session). New containers
default to k8s-file via mcp user's containers.conf.

Also adds stream auth interceptor for the agent gRPC server (required
for streaming RPCs).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

internal/agent/logs.go

@@ -0,0 +1,75 @@
+package agent
+
+import (
+	"bufio"
+	"io"
+
+	mcpv1 "git.wntrmute.dev/mc/mcp/gen/mcp/v1"
+	"git.wntrmute.dev/mc/mcp/internal/registry"
+	"git.wntrmute.dev/mc/mcp/internal/runtime"
+	"google.golang.org/grpc/codes"
+	"google.golang.org/grpc/status"
+)
+
+// Logs streams container logs for a service component.
+func (a *Agent) Logs(req *mcpv1.LogsRequest, stream mcpv1.McpAgentService_LogsServer) error {
+	if req.GetService() == "" {
+		return status.Error(codes.InvalidArgument, "service name is required")
+	}
+
+	// Resolve component name.
+	component := req.GetComponent()
+	if component == "" {
+		components, err := registry.ListComponents(a.DB, req.GetService())
+		if err != nil {
+			return status.Errorf(codes.Internal, "list components: %v", err)
+		}
+		if len(components) == 0 {
+			return status.Error(codes.NotFound, "no components found for service")
+		}
+		component = components[0].Name
+	}
+
+	containerName := ContainerNameFor(req.GetService(), component)
+
+	podman, ok := a.Runtime.(*runtime.Podman)
+	if !ok {
+		return status.Error(codes.Internal, "logs requires podman runtime")
+	}
+
+	cmd := podman.Logs(stream.Context(), containerName, int(req.GetTail()), req.GetFollow(), req.GetTimestamps(), req.GetSince())
+
+	a.Logger.Info("running podman logs", "container", containerName, "args", cmd.Args)
+
+	// Podman writes container stdout to its stdout and container stderr
+	// to its stderr. Merge both into a single pipe.
+	pr, pw := io.Pipe()
+	cmd.Stdout = pw
+	cmd.Stderr = pw
+
+	if err := cmd.Start(); err != nil {
+		pw.Close()
+		return status.Errorf(codes.Internal, "start podman logs: %v", err)
+	}
+
+	// Close the write end when the command exits so the scanner finishes.
+	go func() {
+		err := cmd.Wait()
+		if err != nil {
+			a.Logger.Warn("podman logs exited", "container", containerName, "error", err)
+		}
+		pw.Close()
+	}()
+
+	scanner := bufio.NewScanner(pr)
+	for scanner.Scan() {
+		if err := stream.Send(&mcpv1.LogsResponse{
+			Data: append(scanner.Bytes(), '\n'),
+		}); err != nil {
+			_ = cmd.Process.Kill()
+			return err
+		}
+	}
+
+	return nil
+}