refactor: replace explicit fields with tag-based property system

parse/mentions.go

@@ -6,11 +6,11 @@ import (
 	"slices"
 )
 
-var mentionRegex = regexp.MustCompile(`@([a-z0-9_]+)`)
+var r = regexp.MustCompile(`@([a-z0-9_]+)`)
 
-func Mentions(text string) []string {
+func Mentions(t string) []string {
 	seen := make(map[string]bool)
-	for _, m := range mentionRegex.FindAllStringSubmatch(text, -1) {
+	for _, m := range r.FindAllStringSubmatch(t, -1) {
 		seen[m[1]] = true
 	}
 	return slices.Collect(maps.Keys(seen))