Fix design-vs-implementation gaps found in verification

Critical fixes:
- Wire monitor subsystem to agent startup (was dead code)
- Implement NodeStatus RPC (disk, memory, CPU, runtime version, uptime)
- Deploy respects active=false (sets desired_state=stopped, not always running)

Medium fixes:
- Add Started field to runtime.ContainerInfo, populate from podman inspect
- Populate ComponentInfo.started in status handlers for uptime display
- Add Monitor field to Agent struct for graceful shutdown

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

internal/agent/agent.go

@@ -14,6 +14,7 @@ import (
 	mcpv1 "git.wntrmute.dev/kyle/mcp/gen/mcp/v1"
 	"git.wntrmute.dev/kyle/mcp/internal/auth"
 	"git.wntrmute.dev/kyle/mcp/internal/config"
+	"git.wntrmute.dev/kyle/mcp/internal/monitor"
 	"git.wntrmute.dev/kyle/mcp/internal/registry"
 	"git.wntrmute.dev/kyle/mcp/internal/runtime"
 	"google.golang.org/grpc"
@@ -28,6 +29,7 @@ type Agent struct {
 	Config  *config.AgentConfig
 	DB      *sql.DB
 	Runtime runtime.Runtime
+	Monitor *monitor.Monitor
 	Logger  *slog.Logger
 }
 
@@ -46,10 +48,13 @@ func Run(cfg *config.AgentConfig) error {
 
 	rt := &runtime.Podman{}
 
+	mon := monitor.New(db, rt, cfg.Monitor, cfg.Agent.NodeName, logger)
+
 	a := &Agent{
 		Config:  cfg,
 		DB:      db,
 		Runtime: rt,
+		Monitor: mon,
 		Logger:  logger,
 	}
 
@@ -86,7 +91,8 @@ func Run(cfg *config.AgentConfig) error {
 		"runtime", cfg.Agent.ContainerRuntime,
 	)
 
-	// Graceful shutdown on signal.
+	mon.Start()
+
 	ctx, stop := signal.NotifyContext(context.Background(), syscall.SIGINT, syscall.SIGTERM)
 	defer stop()
 
@@ -98,9 +104,11 @@ func Run(cfg *config.AgentConfig) error {
 	select {
 	case <-ctx.Done():
 		logger.Info("shutting down")
+		mon.Stop()
 		server.GracefulStop()
 		return nil
 	case err := <-errCh:
+		mon.Stop()
 		return fmt.Errorf("serve: %w", err)
 	}
 }