docs(ThreadTitle): add JavaDocs and rename param

Addresses code review by @christolis.

Co-authorized-by: Chris Sdogkos <work@chris-sdogkos.com>
Signed-off-by: Chris Sdogkos <work@chris-sdogkos.com>
Signed-off-by: billpapat <50835814+billpapat@users.noreply.github.com>

Author: billpapat

application/src/main/java/org/togetherjava/tjbot/features/basic/ThreadTitle.java

@@ -1,6 +1,12 @@
-
 package org.togetherjava.tjbot.features.basic;
 
+/**
+ * Represents a thread title, enforcing a maximum length of 60 characters. If an initial title
+ * exceeds this limit, it's truncated at the last word boundary before or at the 60-character mark
+ * to prevent cutting words mid-sentence. If no space is found, it truncates at 60 characters.
+ * Provides a static factory method `withFallback` to create a ThreadTitle, using a fallback title
+ * if the primary title is empty.
+ */
 public record ThreadTitle(String value) {
 
     private static final int TITLE_MAX_LENGTH = 60;
@@ -22,9 +28,9 @@ public ThreadTitle(String value) {
         this.value = threadTitle;
     }
 
-    public static ThreadTitle withFallback(String threadtitle, String fallback) {
-        if (!threadtitle.isEmpty()) {
-            return new ThreadTitle(threadtitle);
+    public static ThreadTitle withFallback(String primary, String fallback) {
+        if (!primary.isEmpty()) {
+            return new ThreadTitle(primary);
         } else {
             return new ThreadTitle(fallback);
         }