feat: add resilience and reliability features for agent subsystems

Added circuit breakers with configurable timeouts for all subsystems (APT, DNF, Docker, Windows, Winget, Storage). Replaces cron-based scheduler with priority queue that should scale beyond 1000+ agents if your homelab is that big.

Command acknowledgment system ensures results aren't lost on network failures or restarts. Agent tracks pending acknowledgments with persistent state and automatic retry.

- Circuit breakers: 3 failures in 1min opens circuit, 30s cooldown
- Per-subsystem timeouts: 30s-10min depending on scanner
- Priority queue scheduler: O(log n), worker pool, jitter, backpressure
- Acknowledgments: at-least-once delivery, max 10 retries over 24h
- All tests passing (26/26)

test_disk_detection.go

@@ -0,0 +1,62 @@
+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"log"
+	"path/filepath"
+	"runtime"
+
+	"github.com/redflag-aggregator/aggregator-agent/internal/system"
+)
+
+func main() {
+	// Get the absolute path to this file's directory
+	_, filename, _, _ := runtime.Caller(0)
+	dir := filepath.Dir(filename)
+
+	// Change to the project root to find the go.mod file
+	projectRoot := filepath.Dir(dir)
+
+	// Test lightweight metrics (most common use case)
+	fmt.Println("=== Enhanced Lightweight Metrics Test ===")
+	metrics, err := system.GetLightweightMetrics()
+	if err != nil {
+		log.Printf("Error getting lightweight metrics: %v", err)
+	} else {
+		// Pretty print the JSON
+		jsonData, _ := json.MarshalIndent(metrics, "", "  ")
+		fmt.Printf("LightweightMetrics:\n%s\n\n", jsonData)
+
+		// Show key findings
+		fmt.Printf("Root Disk: %.1fGB used / %.1fGB total (%.1f%%)\n",
+			metrics.DiskUsedGB, metrics.DiskTotalGB, metrics.DiskPercent)
+
+		if metrics.LargestDiskTotalGB > 0 {
+			fmt.Printf("Largest Disk (%s): %.1fGB used / %.1fGB total (%.1f%%)\n",
+				metrics.LargestDiskMount, metrics.LargestDiskUsedGB, metrics.LargestDiskTotalGB, metrics.LargestDiskPercent)
+		}
+	}
+
+	// Test full system info (detailed disk inventory)
+	fmt.Println("\n=== Enhanced System Info Test ===")
+	sysInfo, err := system.GetSystemInfo("test-v0.1.5")
+	if err != nil {
+		log.Printf("Error getting system info: %v", err)
+	} else {
+		fmt.Printf("Found %d disks:\n", len(sysInfo.DiskInfo))
+		for i, disk := range sysInfo.DiskInfo {
+			fmt.Printf("  Disk %d: %s (%s) - %s, %.1fGB used / %.1fGB total (%.1f%%)",
+				i+1, disk.Mountpoint, disk.Filesystem, disk.DiskType,
+				float64(disk.Used)/(1024*1024*1024), float64(disk.Total)/(1024*1024*1024), disk.UsedPercent)
+
+			if disk.IsRoot {
+				fmt.Printf(" [ROOT]")
+			}
+			if disk.IsLargest {
+				fmt.Printf(" [LARGEST]")
+			}
+			fmt.Printf("\n")
+		}
+	}
+}