feat(03-01): extend TrafficClass to 14 classes with hash-bucketed unknowns

- Replace ClassUnknown with ClassUnknown1-4 (unknown-1 through unknown-4)
- AllClasses() now returns 14 elements
- Add hashBucket() function routing unrecognized traffic deterministically
- Update synth/config.go: NumLayers=14, 4 dissonant unknown tone configs at 862-1047 Hz
- Add TestAllClassesCount and TestHashBucketDistribution tests
- Add TestClassFreqConfigsComplete and TestNumLayersMatchesAllClasses to config_test.go
- Update TestNewBankHas14Layers, TestMixerNoClip for 14 classes
- All classify and synth tests pass

classify/classifier.go

@@ -17,10 +17,9 @@ func NewClassifier(rules []Rule) *Classifier {
 
 // Classify inspects a gopacket.Packet and returns a ClassifiedPacket.
 // It checks ICMP first, then extracts TCP/UDP port info and matches against rules.
-// Per D-03: returns ClassUnknown if no rule matches.
+// Per D-03: returns ClassUnknown1-4 via hash-bucketing if no rule matches.
 func (c *Classifier) Classify(pkt gopacket.Packet) ClassifiedPacket {
 	result := ClassifiedPacket{
-		Class:  ClassUnknown,
 		Length: len(pkt.Data()),
 	}
 
@@ -34,6 +33,7 @@ func (c *Classifier) Classify(pkt gopacket.Packet) ClassifiedPacket {
 				return result
 			}
 		}
+		result.Class = hashBucket(result.DstPort, result.Protocol)
 		return result
 	}
 
@@ -49,6 +49,7 @@ func (c *Classifier) Classify(pkt gopacket.Packet) ClassifiedPacket {
 				return result
 			}
 		}
+		result.Class = hashBucket(result.DstPort, result.Protocol)
 		return result
 	}
 
@@ -64,9 +65,37 @@ func (c *Classifier) Classify(pkt gopacket.Packet) ClassifiedPacket {
 				return result
 			}
 		}
+		result.Class = hashBucket(result.DstPort, result.Protocol)
 		return result
 	}
 
-	// No recognized transport layer -> ClassUnknown per D-03
+	// No recognized transport layer -> hash-bucket per D-03
+	result.Class = hashBucket(result.DstPort, result.Protocol)
 	return result
 }
+
+// hashBucket maps an unrecognized packet to one of 4 unknown traffic classes.
+// Deterministic: same (dstPort, protocol) always maps to the same bucket.
+// ARP and other non-transport packets have dstPort=0, protocol="" -> bucket 0 (ClassUnknown1).
+func hashBucket(dstPort uint16, protocol string) TrafficClass {
+	var protoNum uint16
+	switch protocol {
+	case "tcp":
+		protoNum = 6
+	case "udp":
+		protoNum = 17
+	case "icmp":
+		protoNum = 1
+	}
+	h := uint32(dstPort)*31 + uint32(protoNum)*7
+	switch h % 4 {
+	case 0:
+		return ClassUnknown1
+	case 1:
+		return ClassUnknown2
+	case 2:
+		return ClassUnknown3
+	default:
+		return ClassUnknown4
+	}
+}