fix: disambiguate months and minutes in concise duration format

Both MONTHS and MINUTES resolved to "m" because the concise label
was derived from the first character of the ChronoUnit enum name.
Replace with an explicit label map so months renders as "mo".

Author: demengc

pluginbase-core/src/main/java/dev/demeng/pluginbase/Time.java

@@ -292,6 +292,17 @@ public static String format(final Duration duration, final boolean concise) {
 
     private static final class Unit {
 
+      private static final Map<ChronoUnit, String> CONCISE_LABELS =
+          ImmutableMap.<ChronoUnit, String>builder()
+              .put(ChronoUnit.YEARS, "y")
+              .put(ChronoUnit.MONTHS, "mo")
+              .put(ChronoUnit.WEEKS, "w")
+              .put(ChronoUnit.DAYS, "d")
+              .put(ChronoUnit.HOURS, "h")
+              .put(ChronoUnit.MINUTES, "m")
+              .put(ChronoUnit.SECONDS, "s")
+              .build();
+
       private final long duration;
       private final String formalStringPlural;
       private final String formalStringSingular;
@@ -302,7 +313,7 @@ private static final class Unit {
         this.formalStringPlural = " " + unit.name().toLowerCase(Locale.ROOT);
         this.formalStringSingular =
             " " + unit.name().substring(0, unit.name().length() - 1).toLowerCase(Locale.ROOT);
-        this.conciseString = String.valueOf(Character.toLowerCase(unit.name().charAt(0)));
+        this.conciseString = CONCISE_LABELS.get(unit);
       }
 
       public String toString(final boolean concise, final long n) {