Pin release workflow Java installations

[SkyBlade1978]

Summary

• install pinned Temurin 25 and 8 runtimes in the shared release build and Maven publication jobs
• record the selected target JDK and limit Gradle discovery to the explicitly installed JDKs
• disable automatic Java detection and toolchain downloading
• preserve the existing target/Gradle split and NeoGradle two-invocation lifecycle

Why

The 4.0.16.116051 release passed preflight but failed verifyJava8Toolchain because Gradle selected Ubuntu's preinstalled Temurin 8.0.504 instead of the qualified 8.0.502+7 installed by setup-java. Publication never started and no tag was created.

Compatibility

The explicit path set includes the pinned Java 25 Mavenizer runtime, pinned Java 8 launcher/runtime, target JDK and active Gradle JDK. Duplicate paths are removed. Same-major targets keep their exact target JDK; separate Gradle Java remains conditional. Existing Forge and NeoForge build paths are otherwise unchanged.

Validation

• actionlint 1.7.12
• release workflow isolation contract red-to-green for build and Maven jobs
• exact 1.16 release lifecycle: 127 tests / 33 suites; fresh/reload surface gate; build, Javadocs, artifact and checksum audits
• all three 4.0.16.116051 artifact hashes unchanged
• fork CI, CodeQL and Gradle-wrapper validation passed at cab833a2