Add isQueueAddress() and parseQueueName() helpers to router.go (gt-0q3cg)

Add queue address detection following the same pattern as list address
detection. Includes tests in router_test.go.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/mail/router.go

@@ -60,6 +60,16 @@ func parseListName(address string) string {
 	return strings.TrimPrefix(address, "list:")
 }
 
+// isQueueAddress returns true if the address uses queue:name syntax.
+func isQueueAddress(address string) bool {
+	return strings.HasPrefix(address, "queue:")
+}
+
+// parseQueueName extracts the queue name from a queue:name address.
+func parseQueueName(address string) string {
+	return strings.TrimPrefix(address, "queue:")
+}
+
 // expandList returns the recipients for a mailing list.
 // Returns ErrUnknownList if the list is not found.
 func (r *Router) expandList(listName string) ([]string, error) {

internal/mail/router_test.go

@@ -267,6 +267,52 @@ func TestParseListName(t *testing.T) {
 	}
 }
 
+func TestIsQueueAddress(t *testing.T) {
+	tests := []struct {
+		address string
+		want    bool
+	}{
+		{"queue:work", true},
+		{"queue:gastown/polecats", true},
+		{"queue:", true}, // Edge case: empty queue name (will fail on expand)
+		{"mayor/", false},
+		{"gastown/witness", false},
+		{"queuework", false}, // Missing colon
+		{"list:oncall", false},
+		{"", false},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.address, func(t *testing.T) {
+			got := isQueueAddress(tt.address)
+			if got != tt.want {
+				t.Errorf("isQueueAddress(%q) = %v, want %v", tt.address, got, tt.want)
+			}
+		})
+	}
+}
+
+func TestParseQueueName(t *testing.T) {
+	tests := []struct {
+		address string
+		want    string
+	}{
+		{"queue:work", "work"},
+		{"queue:gastown/polecats", "gastown/polecats"},
+		{"queue:", ""},
+		{"queue:priority-high", "priority-high"},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.address, func(t *testing.T) {
+			got := parseQueueName(tt.address)
+			if got != tt.want {
+				t.Errorf("parseQueueName(%q) = %q, want %q", tt.address, got, tt.want)
+			}
+		})
+	}
+}
+
 func TestExpandList(t *testing.T) {
 	// Create temp directory with messaging config
 	tmpDir := t.TempDir()