chore: delete dead kernel Go code

Remove orphaned channel/message type comments from interfaces.go,
unused roleFilterType() function from pages.go, and stale version
comment from main.go.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/pages/pages.go

@@ -278,7 +278,6 @@ func (e *Engine) parseTemplates() {
 		"toJSON":         toJSON,
 		"eq":             func(a, b string) bool { return a == b },
 		"contains":       stringContains,
-		"roleFilterType": roleFilterType,
 		"esc":            template.HTMLEscapeString,
 		"safeHTML":       func(s string) template.HTML { return template.HTML(s) },
 		"join":           strings.Join,
@@ -919,18 +918,6 @@ func stringContains(haystack []string, needle string) bool {
 	return false
 }
 
-// roleFilterType returns the model_type filter for a given role name.
-func roleFilterType(role string) string {
-	switch role {
-	case "embedding":
-		return "embedding"
-	case "utility":
-		return "chat"
-	default:
-		return ""
-	}
-}
-
 // dict creates a map from alternating key/value pairs for template use.
 func dict(pairs ...any) map[string]any {
 	m := make(map[string]any, len(pairs)/2)