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/agent.go

@@ -100,6 +100,9 @@ func Run(cfg *config.AgentConfig) error {
 		grpc.ChainUnaryInterceptor(
 			auth.AuthInterceptor(validator),
 		),
+		grpc.ChainStreamInterceptor(
+			auth.StreamAuthInterceptor(validator),
+		),
 	)
 	mcpv1.RegisterMcpAgentServiceServer(server, a)