Merge branch 'master' into feature/ext-cache/core-and-caffeine

Resolve conflicts in AGENTS.md, pom.xml and flash-extensions/pom.xml — both
sides added new module/scope/dependency entries in the same spot (ext-validation
from master, ext-cache-core/ext-cache-caffeine from this branch); union kept.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

pom.xml

@@ -39,6 +39,7 @@
         <jmh.version>1.37</jmh.version>
         <junit.version>5.11.0</junit.version>
         <caffeine.version>3.1.8</caffeine.version>
+        <jakarta.validation.version>3.1.1</jakarta.validation.version>
         <build.helper.plugin.version>3.6.0</build.helper.plugin.version>
     </properties>
 
@@ -68,6 +69,16 @@
                 <artifactId>flash-testing</artifactId>
                 <version>${project.version}</version>
             </dependency>
+            <dependency>
+                <groupId>dev.relism</groupId>
+                <artifactId>flash-ext-validation</artifactId>
+                <version>${project.version}</version>
+            </dependency>
+            <dependency>
+                <groupId>jakarta.validation</groupId>
+                <artifactId>jakarta.validation-api</artifactId>
+                <version>${jakarta.validation.version}</version>
+            </dependency>
             <dependency>
                 <groupId>dev.relism</groupId>
                 <artifactId>flash-ext-cache-core</artifactId>