experiment: lower compile target to JDK 22 and test 22 + 25 in CI

FFM (java.lang.foreign) went stable in JDK 22 (JEP 454), so the project may
not actually need a JDK 25 floor. Drop maven.compiler.release 25 -> 22 and
run the CI build matrix on both 22 and 25 to find out. If 22 is green, the
supported floor can drop, widening the addressable audience substantially
(most prod JVMs are on 17/21, not 25).

Experiment only — not for merge as-is; report-driven.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: dfa1

.github/workflows/ci.yml

@@ -9,18 +9,24 @@ on:
 jobs:
   build:
     runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        # Experiment: does the project build + test on JDK 22 (first stable FFM)
+        # as well as 25? If 22 is green, the supported floor can drop from 25.
+        java: ['22', '25']
 
     steps:
       - name: Checkout (with zstd submodule)
         uses: actions/checkout@v4
         with:
           submodules: recursive
 
-      - name: Set up JDK 25
+      - name: Set up JDK ${{ matrix.java }}
         uses: actions/setup-java@v4
         with:
           distribution: temurin
-          java-version: '25'
+          java-version: ${{ matrix.java }}
           cache: maven
 
       - name: Set up Zig

pom.xml

@@ -50,7 +50,7 @@
 
 	<properties>
 		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-		<maven.compiler.release>25</maven.compiler.release>
+		<maven.compiler.release>22</maven.compiler.release>
 		<central-publishing-plugin.version>0.11.0</central-publishing-plugin.version>
 		<maven-gpg-plugin.version>3.2.8</maven-gpg-plugin.version>
 		<maven-source-plugin.version>3.4.0</maven-source-plugin.version>
@@ -164,7 +164,7 @@
 					<artifactId>maven-compiler-plugin</artifactId>
 					<version>3.15.0</version>
 					<configuration>
-						<release>25</release>
+						<release>22</release>
 						<failOnWarning>true</failOnWarning>
 						<compilerArgs>
 							<arg>-Xlint:all</arg>
@@ -176,7 +176,7 @@
 					<artifactId>maven-javadoc-plugin</artifactId>
 					<version>3.12.0</version>
 					<configuration>
-						<release>25</release>
+						<release>22</release>
 						<failOnError>true</failOnError>
 						<failOnWarnings>true</failOnWarnings>
 						<quiet>true</quiet>