ci: run Spotless check at validate instead of apply on compile

Bind spotless:check to the validate phase so builds fail on formatting drift without mutating sources during CI or local package runs. Use spotless:apply locally to fix formatting before commit.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: codeboyzhou

pom.xml

@@ -128,10 +128,11 @@
                 </configuration>
                 <executions>
                     <execution>
+                        <id>spotless-check</id>
                         <goals>
-                            <goal>apply</goal>
+                            <goal>check</goal>
                         </goals>
-                        <phase>compile</phase>
+                        <phase>validate</phase>
                     </execution>
                 </executions>
             </plugin>