feat(nodes): live CPU/RAM/disk monitoring in the node list

- node-agent: internal/metrics — read CPU% (GetSystemTimes), RAM (GlobalMemoryStatusEx),
  disk used%/total (GetDiskFreeSpaceEx) via stdlib kernel32 (no external dep; windows
  build + non-windows stub). Heartbeat now reports cpu_pct/ram_available_mb/disk_used_pct/
  disk_total_gb + ae_running.
- render-svc: heartbeat persists last_disk_pct + disk_total_gb (migration 29); RenderNode
  model + node SELECT/scan carry them.
- admin: rewrite NodesTable to the real RenderNode shape (fixes a pre-existing items/V2Node
  mismatch that left the list empty) + a CPU/RAM/disk bars column + stale-heartbeat flag.
- assets-bundle ingestion: ProjectMediaBundle (jszip) auto-maps project.zip → project/scene
  image/demo/colour + music; PatchProject gains image/full_demo/shared_colors_svg.
- scan: RGBA (4-number) colours recognised + frshare single-int controls detected.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

services/node-agent/cmd/agent/main.go

@@ -37,6 +37,7 @@ import (
 
 	"github.com/flatrender/node-agent/internal/client"
 	"github.com/flatrender/node-agent/internal/config"
+	"github.com/flatrender/node-agent/internal/metrics"
 	"github.com/flatrender/node-agent/internal/runner"
 )
 
@@ -324,10 +325,22 @@ func (a *Agent) heartbeatLoop(ctx context.Context) {
 
 func (a *Agent) sendHeartbeat(ctx context.Context) {
 	status, jobID := a.getStatus()
+
+	// Live host metrics (Windows kernel32; stub elsewhere). CPU samples ~300ms.
+	cpu := metrics.CPUPercent(300 * time.Millisecond)
+	_, ramAvail := metrics.Memory()
+	diskPct, diskTotal := metrics.Disk(a.cfg.WorkDir)
+	aeRunning := a.cfg.AEPath != "" && a.isBusy()
+
 	req := client.HeartbeatRequest{
-		NodeID:       a.cfg.NodeID,
-		Status:       status,
-		CurrentJobID: jobID,
+		NodeID:         a.cfg.NodeID,
+		Status:         status,
+		CurrentJobID:   jobID,
+		CPUPct:         &cpu,
+		RAMAvailableMB: &ramAvail,
+		DiskUsedPct:    &diskPct,
+		DiskTotalGB:    &diskTotal,
+		AERunning:      &aeRunning,
 	}
 	hbCtx, cancel := context.WithTimeout(ctx, 10*time.Second)
 	defer cancel()