feat(06-02): wire --config flag and config.Load into CLI pipeline

- Add configPath string var and --config flag to Cobra command
- Import config and synth packages in main.go
- Call config.Load(configPath) in run() before capture (D-11 fail fast)
- Change runLiveMode and runPcapMode signatures to accept freqCfgs map
- Pass freqCfgs to encode.RunSynthesis in both live and pcap modes

cmd/netsynth/main.go

@@ -16,7 +16,9 @@ import (
 	"github.com/netsynth/netsynth/aggregate"
 	"github.com/netsynth/netsynth/capture"
 	"github.com/netsynth/netsynth/classify"
+	"github.com/netsynth/netsynth/config"
 	"github.com/netsynth/netsynth/encode"
+	"github.com/netsynth/netsynth/synth"
 )
 
 var (
@@ -26,6 +28,7 @@ var (
 	outputPath string
 	bpfFilter  string // NEW: --filter flag (CAPT-05)
 	readPath   string // NEW: --read flag (CAPT-06)
+	configPath string // NEW: --config flag (CFG-03)
 )
 
 func main() {
@@ -42,6 +45,7 @@ func main() {
 	rootCmd.Flags().StringVarP(&outputPath, "output", "o", "", "Output MP3 file path (default: netsynth-<timestamp>.mp3)")
 	rootCmd.Flags().StringVar(&bpfFilter, "filter", "", "BPF filter expression (tcpdump syntax, e.g. \"port 53\")")
 	rootCmd.Flags().StringVar(&readPath, "read", "", "Read packets from pcap file instead of live capture")
+	rootCmd.Flags().StringVar(&configPath, "config", "", "Path to TOML config file (default: auto-discover)")
 
 	if err := rootCmd.Execute(); err != nil {
 		os.Exit(1)
@@ -79,6 +83,12 @@ func run(cmd *cobra.Command, args []string) error {
 		}
 	}
 
+	// Load config (CFG-01 through CFG-05, D-11: fail fast before capture)
+	freqCfgs, err := config.Load(configPath)
+	if err != nil {
+		return err
+	}
+
 	// Resolve output path
 	if outputPath == "" {
 		if readPath != "" {
@@ -89,13 +99,13 @@ func run(cmd *cobra.Command, args []string) error {
 	}
 
 	if readPath != "" {
-		return runPcapMode(cmd)
+		return runPcapMode(cmd, freqCfgs)
 	}
-	return runLiveMode(cmd)
+	return runLiveMode(cmd, freqCfgs)
 }
 
 // runLiveMode runs the live packet capture pipeline.
-func runLiveMode(cmd *cobra.Command) error {
+func runLiveMode(cmd *cobra.Command, freqCfgs map[classify.TrafficClass]synth.FreqConfig) error {
 	// Set up signal handling (Ctrl+C)
 	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
 	defer stop()
@@ -144,7 +154,7 @@ func runLiveMode(cmd *cobra.Command) error {
 	// D-07: Encoding status line
 	fmt.Fprintf(os.Stderr, "Encoding %d windows to %s...\n", len(collectedSnapshots), outputPath)
 	encodeStart := time.Now()
-	if err := encode.RunSynthesis(collectedSnapshots, outputPath); err != nil {
+	if err := encode.RunSynthesis(collectedSnapshots, outputPath, freqCfgs); err != nil {
 		return fmt.Errorf("synthesis failed: %w", err)
 	}
 	encodeElapsed := time.Since(encodeStart)
@@ -161,7 +171,7 @@ func runLiveMode(cmd *cobra.Command) error {
 }
 
 // runPcapMode runs the pcap file processing pipeline (CAPT-06).
-func runPcapMode(cmd *cobra.Command) error {
+func runPcapMode(cmd *cobra.Command, freqCfgs map[classify.TrafficClass]synth.FreqConfig) error {
 	// D-06: bookend start message
 	fmt.Fprintf(os.Stderr, "Reading %s...\n", readPath)
 
@@ -212,7 +222,7 @@ func runPcapMode(cmd *cobra.Command) error {
 	// Encode
 	fmt.Fprintf(os.Stderr, "Encoding %d windows to %s...\n", len(collectedSnapshots), outputPath)
 	encodeStart := time.Now()
-	if err := encode.RunSynthesis(collectedSnapshots, outputPath); err != nil {
+	if err := encode.RunSynthesis(collectedSnapshots, outputPath, freqCfgs); err != nil {
 		return fmt.Errorf("synthesis failed: %w", err)
 	}
 	encodeElapsed := time.Since(encodeStart)