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/runtime/runtime.go

@@ -3,6 +3,7 @@ package runtime
 import (
 	"context"
 	"strings"
+	"time"
 )
 
 // ContainerSpec describes a container to create and run.
@@ -28,7 +29,8 @@ type ContainerInfo struct {
 	Ports   []string
 	Volumes []string
 	Cmd     []string
-	Version string // extracted from image tag
+	Version string    // extracted from image tag
+	Started time.Time // when the container started (zero if not running)
 }
 
 // Runtime is the container runtime abstraction.